Base for a graft polymer, novel graft polymer compositions, solvent and water-reducible coatings incorporating the novel graft polymers, and processes for making them

ABSTRACT

Provides new and improved water-reducible coating compositions and methods of making them. Three preferred processes are disclosed. These differ in the manner of incorporating and chemical nature of an extender polymer. 
     Broadly, the process of the invention is one for forming an aqueous dispersion of a fluent resinous composition of 
     a. a mixture in an organic solvent of 
     (i) an ionizable graft polymer of an epoxy resin and an addition polymerized resin, the addition polymerized resin being bonded to aliphatic backbone carbon atoms of the epoxy resin by carbon-to-carbon bonds, and 
     (ii) an extender resin; 
     b. an aqueous vehicle, and 
     c. an ionizing agent; 
     the ionization present from said combined components being sufficient to establish the components as a dispersion in the aqueous vehicle, and then addition polymerizing a quantity of addition polymerizable monomer, under addition polymerizing conditions, in said aqueous dispersion, the aqueous dispersion serving as a vehicle therefor. 
     In another aspect of the invention, a grafting base is produced by advancing an aromatic epoxy resin in the presence of at least one extender resin and a sufficient amount of an organic solvent to render the initial mixture and grafting base product fluent.

This is a division of application Ser. No. 132,507, filed Mar. 21, 1980,now U.S. Pat. No. 4,399,241 issued Aug. 16, 1983.

RELATED PATENT APPLICATIONS

The subject matter of the present patent application is related to thesubjects matter of several other patent applications, the teachings ofwhich, particularly as identified below, are all incorporated herein byreference.

The earliest-filed application on related technology is Ser. No.685,246, filed May 11, 1976, and now abandoned.

Another patent application on related subject matter is Ser. No.788,611, filed Apr. 18, 1977, which was a continuation-in-part of thefirst-filed patent application, and which has been published as BelgianPat. No. 854,476, granted Nov. 10, 1977, and as German OS No. 2,721,822,published Nov. 24, 1977.

A third application on related subject matter is Ser. No. 788,454, filedApr. 18, 1977, and now abandoned, which was also a continuation-in-partof the first-filed patent application. This third patent application wasabandoned in favor of Ser. No. 793,507, filed May 4, 1977, which ispublished as Belgian Pat. No. 854,523, granted Nov. 14, 1977; as GermanOS No. 2,721,823.1; and as Dutch Patent Application No. 77.05236,published Nov. 11, 1977.

U.S. application Ser. No. 793,507 is a continuation-in-part of Ser. No.788,454. It was abandoned in favor of a continuation application, Ser.No. 038,547, filed May 14, 1979.

A fifth patent application on related subject matter is Ser. No. 29,106,filed Apr. 11, 1979.

FIELD OF THE INVENTION

This invention relates to a process for making a fluent, filterableblended material containing an epoxy resin and a second, extenderpolymer, both of which have aliphatic backbone carbon atoms at whichgrafting can take place, and processes for making such blends.

The invention is also concerned with the processes for making novelgraft polymer compositions from these blends, and to coatingcompositions utilizing these novel graft polymer compositions, and tothe products thus obtained.

In a particular and preferred embodiment, the invention is concernedwith sprayable, water-reducible coating compositions suitable forapplication to the interior of metal containers, such as cans, usefulfor packaging beverages.

BACKGROUND OF THE PRESENT INVENTION

There is a continuing demand for improved types of coating compositions,both solvent-based and water-reducible. More specifically, there is acontinuing and growing demand for water-reducible, sprayablecompositions suitable for application to metal surfaces intended to comein contact with beverages, and especially, for lining the interior ofbeverage cans.

Of the patent applications identified above, Ser. Nos. 685,246, 788,611and 793,507 describe novel, sprayable, water-reducible coatingcompositions that are particularly useful for lining beverage cans. Thecompositions described have superior metal-coating characteristicsderived from an epoxy resin component, and economy contributed by avinyl resin component. These important characteristics are available,moreover, in compositions that when cured meet the many demanding testswith which any beverage can lining composition is confronted.

Nevertheless, the need for continuing improvement in functionalcharacteristics, in economy, and in properties that facilitatecompliance with environmental protection legislation, particularly withrespect to the release of solvents to the atmosphere, indicate the needfor still further technological change and progress.

The first-filed application above, Ser. No. 685,246, in one preferredembodiment, discloses a process for preparing a curable resinouscomposition having an Acid Number of at least 30, by reacting togetherat 90° C. to 130° C. an aromatic 1,2-epoxy diepoxide resin having amolecular weight above 350 and addition polymerizable monomer of whichfrom 10% to 80% by weight is an acrylic acid, the diepoxide resin beingpresent in sufficient quantity to provide from 10% to 90% by weight ofthe initial reaction mixture, in the presence of a free radicalinitiator of the benzoyl peroxide type. During the reaction there issimultaneous addition polymerization of the monomer through itsethylenic unsaturation and grafting of addition polymer to the epoxyresin. The graft polymer is characterized by the substantial absence ofhydrolyzable functional groups. The ionizability of the reactionmixture, by reason of its acid functionality, is sufficiently high toeffect stable dispersion of the product in an aqueous ionizing medium.

In a preferred embodiment, an aromatic diepoxide such as a polyglycidylether of bisphenol A is reacted with a mixture of addition polymerizablemonomers containing a major amount of methacrylic acid. The epoxy resinhas a molecular weight of at least 1,000, and provides from 30% to 90%of the initial reaction mixture. The reaction takes place in thepresence of benzoyl peroxide at a temperature of 90° C. to 130° C., toeffect addition polymerization of the monomer and to produce a graftpolymer of addition polymer to the diepoxide having an Acid Number of 30to 150 or more, preferably 70-90. The reaction product may be dispersedin a basic aqueous medium, to form a water-reducible coatingcomposition. Generally a cross-linker is added, such as an aminoplast,and curing is effected in an oven. Most preferably the epoxy resin has amolecular weight in the range 4,000 to 10,000 and provides 50% to 90% ofthe initial reaction mixture.

As is more particularly pointed out in patent application Ser. No.788,611, the resinous reaction product produced contains three polymericcomponents, namely, the graft polymer, ungrafted epoxy resin, andungrafted addition polymer.

As is pointed out in Ser. No. 793,507, the initial epoxy resin, that isemployed in the graft polymer production process, may be terminated toeliminate part or all of the terminal epoxy groups, to eliminate estergrafting at the terminal epoxy groups. Elimination of the terminal epoxygroups also permits the efficient use of a wider variety ofperoxide-type free radical initiators, over a broader reactiontemperature range, than would otherwise be the case.

As is disclosed in these prior applications, in order to make acceptablewater-reducible coating compositions, the addition polymerizable monomercomprises a major proportion of an unsaturated carboxylic acid,preferably either acrylic or methacrylic acid. Sufficient acid isemployed so that the Acid Number (NV, i.e., based on non-volatiles) ofthe reaction product is from about 30 to 200. The ionizability ofcompositions prepared in accordance with these several patentapplications is based on the acid functionality of the graft polymer andof the ungrafted addition polymer. When the carboxyl groups are ionizedby the addition of such a composition to an aqueous vehicle containingan amine or other fugitive base, an aqueous dispersion is produced thatis water-reducible. Such dispersions are stable over long storageperiods even at somewhat elevated temperatures, and remain free fromgelation and precipitation. Only slight changes occur in pH levels andviscosities, indicating very little change in composition.

The reaction products of these prior applications appear to haveremarkable properties. Their contents of ionized polymers are believedto serve as the means by which the ungrafted, nonionized epoxy resincomponent is kept in stable suspension.

For sanitary coating applications of the prior applications, Ser. Nos.788,611 and 793,507, the preferred compositions are obtained frominitial reaction mixtures in which the solids are derived 50% or more byweight from an epoxy resin having a molecular weight of at least 4,000,and the balance from addition polymerizable monomer of which the majorproportion is acrylic or methacrylic acid. In a more preferredembodiment of such a sprayable sanitary coating composition, the solidsof the reaction mixture are derived from an epoxy resin that contributesfrom 60% to 90%, and preferably about 80%, by weight of the solids, thebalance being a monomer mixture of methacrylic acid, styrene, and ethylacrylate, where the acid is the predominant monomer. Preferred sanitarycoating compositions produced from such reaction mixtures have AcidNumbers (N.V.) in the range from about 80 to about 90 and preferablyabout 85.

While resinous coating compositions of these kinds have excellentfunctional characteristics and other highly desirable properties, thehigh content of epoxy resin increases the cost. It would therefore behighly desirable to find some way to produce functionally equivalentmaterials, at lower cost.

Still another important consideration is the release of solventmaterials into the atmosphere. In the process of making the reactionproducts of the patent applications described above, it has beencustomary to use liquid organic solvent to facilitate handling duringthe manufacturing process and to improve application properties.

In the most preferred embodiment of the invention, for example, it hasbeen customary to use two different solvents, a first solvent in whichthe epoxy resin, the graft polymer, and the addition polymer are allsoluble, and a second solvent that can dissolve the addition polymerproduct and that can solvate the addition polymer side chains of thegraft polymer. The solvents remain with the resinous reaction productafter it is dispersed by the addition of water and a fugitive base, andmore may be added to adjust application characteristics. A typical ratioof total organic solvent to total film-forming resinous solids (OS/S) isabout 0.9, in a formulated, sprayable, sanitary coating composition.Consequently, when an applied coating is cured, which is usuallyaccomplished by heating, the solvent is driven off and ordinarilyescapes into the atmosphere. With the present concern over the releaseof organic solvent materials into the atmosphere, it is highly desirablethat coating compositions be prepared in such manner as to reduce theamount of organic solvent liquid present to the smallest feasibleamount.

In the fifth patent application referred to above, Ser. No. 29,106,filed Apr. 11, 1979, coating compositions and processes for making themwere disclosed that advanced the art by providing compositions havingthe functional characteristics adverted to in connection with theinventions described above in the other co-pending applications, butcontaining a greater proportion of addition polymer, thereby permittingeconomies, and also containing a smaller proportion of volatile organicsolvent, thereby facilitating compliance with environmental protectionlaws.

Improved water-reducible coating compositions are made in accordancewith this application by polymerizing in situ, in an aqueous dispersionof a resinous reaction product produced in accordance with a process ofone of the earlier-filed patent applications described above, a limitedquantity of addition polymerizable monomer containing ethylenic (vinyl)unsaturation, such as styrene. The result is to reduce substantially thepercentage of the final composition solids represented by the initialepoxy resin, and to increase substantially the percentage of the finalcomposition solids formed from ordinarily much less expensive additionpolymerizable monomer. The resulting increase in solids and decrease inthe proportion of solvent are important advantages. Moreover, theproportion of solvent may be further reduced by the addition of waterduring or after the in situ addition polymerization reaction. A typicalOS/S ratio would be about 0.7, for a fully formulated sprayable sanitarycoating composition.

The addition to the dispersed, graft polymer-containing resinousreaction product, of vinyl polymers formed by the in situ polymerizationreaction, offers a still further advantage, namely, an improved set ofphysical and chemical characteristics for certain applications,important among which is improved resistance to weathering.

BRIEF SUMMARY OF THE INVENTION

In its broadest aspects, this invention provides new and improvedpolymeric products and processes for making them, and new and improvedcoating compositions and processes for making them, especiallywater-reducible coating compositions that are characterized by desirableapplication and functional properties, very low solvent release to theatmosphere, and economical formulation.

A first preferred mode of the process of the invention involves thesesteps:

1. Forming a fluent blend of an aromatic epoxy resin with an extenderpolymer in an organic solvent, preferably substantially free fromparticulate matter. The extender polymer may be a (Type A, saturated)material such as:

a. polystyrene;

b. low molecular weight polyethylene;

c. a styrene-acrylate copolymer;

d. an ethylene-vinyl acetate copolymer;

e. a hydroxyl-terminated polyester of polyurethane;

f. styrene-acrylonitrile copolymers;

g. almost any hydrocarbon resin;

h. a second epoxy resin, selected for its properties, cost, or the like,or

i. a mixture of one or more of these.

2. Advancing the epoxy resin with a diphenol or other polyfunctionalextender, generally at a temperature in the range from 130° C. to 250°C. The extent of the advance is controlled so that the mix remainstractable. When a polyglycidyl ether of bisphenol A is advanced byreaction with bisphenol, a temperature of about 180° C. is a usefulreaction temperature. However, when a hydroxyl-terminated polyester isemployed as all or a substantial proportion of the extender, then ahigher temperature, about 220° C., is used. The advancement in any caseis arrested at a desired stage, by cooling, reacting some or all of theepoxy groups, or the like.

3. Adding ethylenically unsaturated monomer together with at least 3% byweight of the monomer of benzoyl peroxide, or equivalent peroxide-typeinitiator, and raising the temperature as needed to activate theinitiator. In a preferred embodiment, the monomer contains enough of anacrylic acid to contribute at least 5% by weight of carboxyl (COOH)groups to the total solids present. There must be enough ionizability,through acid or base functionality, that the material can be establishedas a dispersion in a basic aqueous vehicle.

4. Adding water and an ionizing agent, to disperse all of the polymersolids in the aqueous vehicle

5. Performing a vinyl polymerization in situ, preferably with styrene orwith styrene and an acrylic acid.

Sufficient ionizability must still be present to permit dispersionformation.

This process produces a dispersion that may be further diluted withwater. It may also be formulated with pigments, a cross-linking agent,and the like, for application as a decorative and protective coating.

Steps 1 and 2 above prepare a grafting base, by blending a 1,2-epoxyresin having an epoxy equivalent weight (EEW) of at least 180-200, andpreferably 500 or more, with a second, extender polymer, mixing theresin and the polymer with an organic solvent to form a fluent blend,and then advancing the epoxy resin in the presence of the extenderpolymer. The epoxy resin is advanced by reacting it with apolyfunctional compound that adds to the epoxy resin at its epoxidegroups, to advance the resin to a higher molecular weight. Thepolyfunctional compound is preferably either a polyhydroxy compound or apolycarboxylic acid.

The grafting base may be one prepared in the manner described in thepreceding paragraph, or it may be one prepared by blending together in asolvent an epoxy resin of suitable epoxy equivalent weight, preferablyabove 500, and more preferably not substantially below 2,000, and theextender polymer.

In a second preferred mode of the process of the invention, the extenderpolymer employed contains ethylenic unsaturation (Type B, unsaturated).It therefore offers convenient points of attachment for the later-addedmonomer, so that side chains may develop at each ethylenicallyunsaturated site. Looked at another way, it could be said thatcopolymerization occurs. Suitable such extender polymers includepolybutadiene, unsaturated polyesters, unsaturated alkyds, polyisoprene,butadiene-styrene polymers, and acrylated resins that are ethylenicallyunsaturated. Except for the selection of the extender polymer, the stepsare essentially the same as stated above. However, the chemicalstructures in the resulting grafting base are more complicated anddiverse.

Both the epoxy resin and the extender polymer components of the graftingbase should provide aliphatic backbone carbon atoms having one or twohydrogens bonded thereto in the ungrafted state, at which grafting canoccur in the third, grafting step. Also, the extender polymer should beselected to be a film-former that remains in the film after baking at atemperature of at least 375° C. (190° C). Preferably it is soluble inthe solvent used. Generally, it is inert to the epoxy resin and to theadvancing agent but it may simply be relatively inactive as to the epoxyresin and substantially less reactive to the advancing agent than theepoxy resin at the temperature used for advancement, which generally isin the range from about 120° C. to about 200° C.

The second step of advancing the epoxy resin includes the step ofarresting the advancement. This may be either an active step, involvingcooling, for example, or a passive step, i.e., complete consumption ofthe reactants, or a combination of both.

The third step involves polymerizing ethylenically unsaturated monomerin the presence of the grafting base, and in the presence of aninitiator. When the extender polymer is a Type A, saturated polymer,this step is carried out in the presence of at least 3% and preferablymore than 4% by weight, based on the monomer weight, of benzoyl peroxide(BPO) or other suitable peroxide-type initiator that has the abilitysimultaneously to initiate (1), addition polymerization of the monomerthrough its ethylenic unsaturation, and (2), graft polymerizaton ofaddition polymer to aliphatic backbone carbon atoms of the epoxy resinand of the extender polymer. Suitable initiators must be capable ofinitiating addition polymerization through ethylenic unsaturation. Whenextender polymer is saturated, the initiator also must have the abilityto abstract hydrogen from a backbone carbon, to permit carbon-to-carbongrafting to occur.

When the extender polymer is Type B, unsaturated, the sameconsiderations apply, subject to the proviso that less than 3% of theinitiator may be needed since the reaction involves the unsaturatedextender polymer as well as the epoxy resin. Consequently, the amount ofinitiator may be substantially as low as would suffice for initiatingthe addition polymerization and abstracting hydrogen and causinggrafting in that manner. However, the use of a peroxide-type, hydrogenabstracting initiator, in an amount of at least 3% BPO or equivalent, ispreferred, it is believed that this preferred mode induces grafting onboth the epoxy resin and the extender polymer, whether the extenderpolymer is saturated or unsaturated.

The products of the process described in the preceding paragraph (thethird step), like the grafting base, are novel and are useful in and ofthemselves. For example, the grafting base and these resinous reactionproducts can be formulated into useful solvent-based coatingcompositions for either air drying or baking.

Provided that the third step product contains a sufficient number ofionizable sites so that it is emulsifiable, as is preferred, it can bedispersed, as in the fourth step, in an aqueous vehicle containing anionizing agent to make a water-reducible, dispersion-type coatingcomposition. Such an aqueous dispersion is also a useful vehicle inwhich vinyl monomer can be polymerized in situ, as in the fifth step, toincrease the solids content of the dispersion, and at the same time todecrease the relative proportion of organic solvent. The end product ofthis fifth process step is a water-reducible aqueous dispersion that issuitable for a variety of coating applications. In preferredembodiments, such compositions are sprayable and are useful for liningbeverage cans.

A third preferred embodiment of the invention involves a variation inthe order of the steps, as follows:

1. Advancing the epoxy resin (if necessary).

2. Addition polymerizing-grafting (as in Step 3 above).

3. Dispersing in an aqueous vehicle (as in Step 4 above).

4. Adding to the dispersion an extender resin.

5. Performing a vinyl polymerization in situ.

This variation embodiment of the invention is less preferred. If theextender polymer is saturated, there is less opportunity for grafting tooccur, although some grafting seemingly does occur in the fifth, finalstep. If the extender polymer is unsaturated, then grafting will occur.This third process mode can of course be combined with each of the twoprocess modes already described, which also can be combined with eachother. As described in greater detail hereafter this variant processembodiment also produces water-reducible products that can be formulatedinto valuable coating compositions.

DETAILED DESCRIPTION OF THE PRIOR INVENTIONS; PROCESS AND PRODUCT

The prior inventions are most easily understood from a description ofone specific preferred embodiment.

When making a sanitary coating composition in accordance with onepreferred embodiment of one of the earlier patent applications describedabove, for example, Ser. No. 788,611, 70 to 80 parts by weight of anaromatic 1,2-epoxy resin are placed in a reaction vessel with a smallamount of a solvent, such as, for example, 2-butoxy-ethanol-1. The epoxyresin may be purchased and used as is, in which case an initial epoxyequivalent weight (EEW) of about 4,000 is preferred, or alternatively, alow EEW resin may be reacted further with bisphenol A to produce anepoxy resin having the desired EEW of about 4,000.

A mixture of monomers containing ethylenic unsaturation is thenprepared. In one preferred embodiment, this mixture is formed from about65 weight percent methacrylic acid, 34 weight percent styrene, and 1weight percent ethyl acrylate. Benzoyl peroxide (BPO) is incorporated inthe mixture in an amount equivalent to about 6.7% of the monomer mixtureby weight. This mixture is then added to the reaction vessel containingthe epoxy resin over a period of time, at a temperature in the rangefrom 110° C. to about 130° C., preferably about 115° C. to 120° C., andmore preferably about 118° C., to permit the reaction to go forward.Sufficient butanol and 2-butoxy-ethanol-1 are added to facilitateagitation.

It is very difficult to make an accurate analysis of the reactionproduct that is obtained. However, current indications are that on a drysolids basis, the reaction product contains three different components,as follows:

1. about 38% of unreacted epoxy resin;

2. about 7% by weight of ungrafted addition polymerized monomer, and

3. about 55% of a graft polymer, in which 65% of the original additionpolymerizable monomer has polymerized and grafted to about 53% of theoriginal epoxy resin.

All of these values are approximations due to limitations in analyticaltechniques.

Studies on this reaction and the product produced indicate that graftingtakes place at aliphatic backbone carbons of the epoxy resin that haveeither one or two hydrogens bonded thereto in the ungrafted state.Pictorially, bonding takes place at one of the carbons indicated by thearrows below: ##STR1## The graft polymer product consists of an epoxyresin molecule, of about 8,000 molecular weight, grafted with, on thebasis of statistically averaged information, about two short chains ofaddition copolymer per molecule of epoxy resin, the molecular weight ofeach chain being about 1,500, so that the molecular weight of the graftpolymer itself is about 11,000. This structure is one that can berepresented generally as follows: ##STR2##

Gel permeation chromatography indicates that the molecular weight of theunreacted epoxy resin in the final product is somewhat lower than thatof the initial epoxy resin, indicating that higher molecular weightepoxy resin tends to be grafted preferentially. This probably occursbecause there are more grafting sites per molecule in the highermolecular weight epoxy resin molecules. The available analytical dataalso indicates that during the polymerization of the mixture of additionpolymerization (vinyl) monomers, very little homopolymer is formed, andthat the ungrafted acrylic copolymer has a longer chain length (highermolecular weight) than the grafted acrylic copolymer.

The resinous reaction product, which is a mixture of the threecomponents described above, has an Acid Number of about 85, and apercent oxirane oxygen content, as determined by the analytical methoddescribed in the patent applications described above, of about 0.35, orless.

During the manufacturing process, the solvent content of the product isadjusted periodically so that in this preferred embodiment, the finalproduct is about 58%-60% by weight solids, the balance being a solventsystem consisting of a mixture of n-butanol and 2-butoxy-ethanol-1.

To prepare a coating composition useful for spray application to cansfor beverages, the resinous reaction product is mixed with deionizedwater and a fugitive base, which in the preferred embodiment is dimethylethanolamine. Sufficient water is employed so that the non-volatilescontent of the composition is about 21% to 24%, with a pH of about 7.8.About 10% to 11% by weight of the initial epoxy resin of a suitablecrosslinking aminoplast resin, such as, for example, Cymel 370, aproduct of American Cyanamid Company, is then added. After thoroughmixing, the resulting dispersion remains stable on storage indefinitely.It sprays readily with particularly good application properties. Itcures rapidly on baking. The coatings produced are bland, and do notimpart any undesirable organoleptic property or haze to a cannedbeverage or other food product.

The difficulty in analyzing the resinous reaction product obtained fromthe graft polymerization step cannot be overemphasized. Moreover, thecomposition of the product obtained depends upon the initial molecularweight of the epoxy resin, the proportions of the reactants, and theamount of BPO or equivalent initiator employed, among other factors.Consequently, for the preferred embodiment described above, theanalytical data reported should be understood to be approximate. Theproportion of the molecular weight of the graft polymer that iscontributed by the addition polymer side chains is particularlydifficult to determine, but probably is in the range from about 16% toabout 20%, for this particular, preferred embodiment.

One of the interesting properties observed, as to the resinous reactionproduct, is that its Tg is about 30° C.-65° C. This compares with muchhigher Tg values for the initial epoxy resin component; for a copolymerthat is prepared by the addition polymerization of a monomer mixturesuch as was used; and for a mixture of the initial epoxy resin with sucha copolymer; the Tg values for these being, respectively, generally inthe range from about 80° C. to 85° C.; about 110° C.; and about 75° C.to 80° C.

For other embodiments of the invention than the can coating embodimentjust described, the particular components employed, and theirproportions, for making the resinous reaction product containing thegraft polymer, are subject to a broad discretion, depending upon theintended application. The epoxy resin may have a molecular weight in therange from about 350 to about 40,000 or higher, the limiting factorbeing the ability to handle the epoxy resin on a practical basis. Theamount of epoxy resin may be in the range from about 5% by weight toabout 95% by weight of the initial reaction mixture, dry solids basis.

To make a preferred sprayable sanitary coating composition, themolecular weight of the epoxy resin, preferably a diglycidyl ether ofbisphenol A, generally is in the range from 4,000 to 20,000, or higher,or more preferably for practical manufacturing processing, in the rangefrom about 8,000 to 12,000 or so. The proportion of epoxy resin in theinitial reaction mixture preferably is from about 60% to about 90% byweight, and more preferably, 70% to 80%. Sufficient methacrylic acid orthe equivalent should be employed in the monomer component so that theAcid Number of the resinous reaction product, based on solids, is in therange from 80 to 90. For use it is dispersed in water with an amineionizing agent, and preferably a cross-linker is added. The coating isbaked to cure it, and to drive off fugitive ionizing agent.

For all of these and other coating applications, the amount of benzoylperoxide or other equivalent initiator employed in the grafting-additionpolymerization reaction should be above 3% by weight based on themonomer, preferably more than 4% and most preferably in the range fromabout 6% to 7%. This permits the use of reaction temperatures in therange from about 110° C. to about 130° C., preferably about 115°-120°C., for efficient operation. If the epoxy resin is terminated, however,higher reaction temperatures and other peroxide-type initiators can beemployed. If active epoxy groups are present, temperatures above about130° C. tend to favor ester formation, rather than carbon-to-carbongrafting.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

The following description, until indicated otherwise, refers to thefirst, preferred embodiment of the process of this invention.

FIRST PREFERRED EMBODIMENT Steps 1 and 2 The Grafting Base

To make the novel grafting base, an aromatic or aliphatic epoxy resin,preferably an aromatic 1,2-epoxy diepoxide resin is blended with theextender polymer and organic solvent. The term "epoxy resin" as usedherein is intended to encompass those aliphatic and/or aromatic resinswhich may be defined as polyethers containing terminal oxirane groups.In the usual and preferred case, the epoxy resin will be a diglycidylpolyether of bisphenol A or a similar diphenol, in which the terminaloxirane groups are separated by alternating aromatic and aliphaticunits.

The two polymeric materials, either before or after being blendedtogether, are generally mixed with an organic solvent which facilitateshandling of the blend, and preferably in which the blend is soluble.This mixture should be fluent, i.e., easily stirred, and while it may bea slurry, it preferably forms a clear solution free from particulateresinous material. The terms "fluent" and "tractable" refer to theability to mix on a practical basis with conventional mixing equipmentsuch as a turbine or propellor mixer. At 180° C., this means that theviscosity would be about 200,000 cps. maximum.

The epoxy resin is then advanced by reaction with a polyfunctionalcompound that adds to the epoxy resin at its epoxide groups, to increaseits epoxide equivalent weight (EEW). This polyfunctional advancing agentgenerally will either not react with the extender polymer, or will reactpreferentially with the epoxy resin.

The extender polymer often is a saturated hydrocarbon polymer, such as alow molecular weight polyethylene, i.e., a polyethylene oil, grease, orwax, or polystyrene, polyisobutylene, or the like. This polymer, likethe epoxy resin, preferably is one that has aliphatic backbone carbonsthat have either one or two hydrogens bonded thereto in the ungraftedstate. Thus, low molecular weight hydrocarbon polymers such as thosementioned above, and in addition, other low molecular weight polymerssuch as polypropylene, copolymers of polyethylene, copolymers ofpolypropylene, poly(4-methylpentene-1), poly-alpha-methylstyrene, andother such hydrocarbon polymers are suitable for use.

Also suitable are acrylate polymers and copolymers such asstyrene-acrylate copolymers, styrene-allyl alcohol copolymers,hydroxy-terminated polyurethane resins, and ethylene-vinyl acetatecopolymers. Hydrocarbon resins such as polyindene, naphthalene polymers,and the like, are also useful. Polycoumarone and coumarone-indene resinsmay also be used.

The extender polymer may also be an epoxy resin, selected for examplefor special properties or for low cost. Thus expoxidized polybutadienemay be used. If desired, when an epoxy resin is used as the extender,some or all of the epoxy groups may be removed by chemical modification.

If the extender resin is one that is reactable with epoxy groups attemperatures on the order of those used in the advancement reaction, aswould be the case with an acid-containing polyester, then a loweradvancement temperature might be required. The modification of epoxygroups with benzoic acid or the like, in the presence of an extenderresin such as a polyester, might lead to cross-linking to the epoxygroup sites.

The polyfunctional compound that is employed to advance the epoxy resinmay be an aromatic polyhydric alcohol, preferably a polynuclearpolyhydroxy phenol; an aliphatic polyhydric alcohol; or a polycarboxylicacid, either of the saturated aliphatic kind or the cyclic unsaturatedor aromatic kind. Particularly suitable aromatic polyhydric alcoholsinclude bisphenol A, bisphenol F, novolac resins, and materials such aspolyhydroxy diphenyl sulfone. Suitable aliphatic polyhydric alcoholsinclude ethylene glycol, glycerol, butanediol, erythritol, polyethyleneglycol, polypropylene glycol, including specifically such glycols astriethylene glycol, and the like. Suitable polycarboxylic acids and acidanhydrides are those of adipic, azelaic, sebacic, and succinic acids.Suitable cyclic acids include tetrahydrophthalic acid, hexahydrophthalicacid, and phthalic acid.

The organic solvent that is employed may be added, or, if the epoxyresin and the hydrocarbon polymer happen to be available in solutionform on a commercial basis, it may be that the solvent already presentwill suffice. The epoxy resins are often available in liquid form at lowmolecular weights, or in solution form, at either low or moderately highmolecular weights. Otherwise, a wide variety of solvents can be employedto dissolve or slurry the resins. A particularly preferred solvent is2-butoxy-ethanol-1. This material is also a good solvent for many of thehydrocarbon extender polymers (both saturated and unsaturated) that aresuitable for use in the present invention.

The extender polymer selected must be capable of dissolution in asolvent. This places an inherent limitation on the molecular weight ofmany of the extender polymer materials, such as, for example,polyethylene and polypropylene.

While the epoxy resin may have an EEW as low as about 180 to 200, such aresin does not have many aliphatic backbone carbon atoms suitable forgrafting. Accordingly, it is preferred that the epoxy resin be apolyglycidyl ether of a bisphenol, preferably a diglycidyl ether ofbisphenol A, and have an EEW of at least 500, and more preferably, notsubstantially below 2,000. Such preferred epoxy resins provide a numberof available grafting sites.

The epoxy resin may contribute from 10% to about 90% or more by weightof the solids initially present in the mixture for making the graftingbase. The balance of the solids for the grafting base is contributed bythe extender polymer or by a mixture of suitable such polymers.

As a practical matter, at present water-reducible coating compositionsfrom the fifth step would be designed for use for coating metalsurfaces, because of the good wetting, adhesion, and barriercharacteristics imparted by the epoxy resin. Consequently, in order thatthe characteristics of the epoxy resin may be apparent in the finalcoating composition products, the epoxy resin employed generally shouldcontribute at least 5% and preferably at least 20% by weight of thetotal solids in the final product.

Generally, the final product (from step 5) may contain as little as 5%by weight of solids derived from the initial epoxy resin for suchapplications as a wood paint. For metal protective and decorativecoatings, the epoxy resin should contribute at least 20% and preferablyabout 25%, and more preferably a minimum of 30% to 40% of final product(from step 5) solids, depending on the properties desired and thosecontributed by the extender polymers, with an upper limit of about 60%representing all that is required for the attainment of most desirablefunctional properties. Greater amounts of epoxy resin may be present, ofcourse.

The desirable functional properties imparted by the epoxy resin includenot only wetting and adhesion properties, but also the ability to formgood barrier films, as between a can and its contents. Moreover, if theadhesion to the substrate is strong enough, the coating will act asthough it were flexible (even though in fact it may not be). This isimportant in some types of fabrication where the substrate is coatedfirst, then shaped mechanically while coated. Obviously the demands oncoatings in such applications are severe. For sprayable sanitary coatingcomposition materials (from step 5), an epoxy resin contribution tototal solids of from 30% and preferably 40% to 60% is feasible, and withcareful formulation and for good economy, from 45% to 50% is preferredat present, and represents an important formulating accomplishment ofthe present invention.

These final product figures are important with respect to the initialproportion of epoxy resin that must be present in the grafting base.

The proportion of total solids present to organic solvent in the initialmixture of epoxy resin and extender polymer, from which the graftingbase is made, may be as little as is required to permit suitablehandling for practical manufacturing operations. However, while thegrafting base must be fluent or tractable to permit it to be worked inpractical manufacturing operations, this characteristic can be derivedfrom the use of an elevated temperature and not just from the use ofsolvent alone. The proportion of solvent used will depend upon thecharacteristics of the epoxy resin and of the extender polymer employed.Generally the practical limit is about a 60% concentration of solids inthe solvent. While lower solids concentrations are usable, one of theobjectives of the invention is to reduce the organic solvent content ofthe final product, and accordingly, a preferred operating range forsolvent concentration in the grafting base is from about 40% solvent toabout 60% solvent.

The third step of the process of the present invention, described below,is a grafting reaction. One feature of this reaction is the use of anunusually high proportion of free radical initiator relative to additionpolymerizable monomer that is used in the reaction. The free radicalinitiator must be one that has hydrogen abstraction capability, toinduce the formation of carbon-to-carbon bonding at aliphatic backbonecarbons of the advanced epoxy resin and of the extender polymer, in thegrafting base. The preferred free radical initiator for this purpose isbenzoyl peroxide.

The benzoyl peroxide is employed at an elevated temperature in order toactivate it. A temperature of 110° C. to 130° C. is preferred, and amore preferred operating temperature is one in the range from about 115°C. to about 120° C. In this operating temperature range, the benzoylperoxide decomposes, forming, as one by-product, benzoic acid. There isa tendency for the benzoic acid to react with the epoxy groups of theepoxy resin, to form epoxy esters, and if the monomer used includes acarboxylic acid, it also may form esters.

To avoid or reduce ester formation and particularly, ester grafting, theepoxy resin may be reacted, when preparing the grafting base, withenough chemical terminating agent to eliminate the epoxy groups in partor substantially completely. Materials that are generally useful asterminating agents for the epoxy groups include the phenols, many of thecarboxylic acids, primary and secondary amines, mercaptans, alcohols,and water. Ethylenically unsaturated terminating agents can be used, andwill lead to addition polymerization reactions during the subsequentgrafting step.

Bisphenol A is a preferred terminating agent for advancing the epoxyresin. For example, slightly less than 64 weight parts of Dow DER 333liquid epoxy resin per 36 weight parts of bisphenol A, to about 60 partsof the DER 333 liquid epoxy resin per 40 weight parts of bisphenol A,represents a useful range for these particular reactants. One preferredterminated epoxy resin is a diglycidyl ether of a bisphenol, wherein themolar ratio of the diglycidyl ether to the bisphenol is from about 1.7to about 1.5.

Other hydroxy materials that are useful as terminating agents includethe cresols and the xylenols. Saturated fatty acids and aromaticmonocarboxylic acids, such as benzoic acid, are particularly usefulterminating agents, but like the monohydroxy compounds, they terminatewithout advancing the resin. They are thus useful in the presentinvention for terminating an epoxy resin that is at a desired molecularweight, and if used, preferably are used prior to the grafting reaction.Ordinarily the fatty acids can be used in a variety of commericial formsand need not be highly purified. However, acids such a palmitic, lauric,myristic, and stearic are very useful, in either refined form or ashighly purified acids.

The primary and secondary amines are also useful terminating agents, andparticularly, hydroxyl amines such as, for example, ethanolamine anddiethanolamine. Tertiary amines are generally not suitable terminatingagents, since they lack the presence of a labile hydrogen atom reactablewith the epoxy group.

Some representative grafting base compositions, in terms of the solidspresent, are described in Tables 1A and 1B below. Each of the graftingbases described in these tables can be used in the practice of theinvention. If at least about 40% by weight of the solids present in thefinal product are to have been contributed by the initial epoxy resin,then in practice careful control must be exercised in the grafting(third) step and in the in situ polymerization (fifth) step as to theamount of contributed to total solids by each of these steps.

                  TABLE 1A                                                        ______________________________________                                        Representative Grafting Base Solids Compositions                                                  Extender                                                  Epoxy Resin Component                                                                             Polymer Component                                         Grafting                                                                              % by Weight         % by Weight                                       Base    Based on            Based on                                          No.     Solids     Identity*                                                                              Solids   Identity*                                ______________________________________                                        1-1     95         A        5        K                                        1-2     95         A        5        L                                        1-3     95         A        5        N                                        1-4     94.4       B        5.6      O                                        1-5     85         B        15       N                                        2-1     80         A        20       K                                        2-2     80         A        20       L                                        3-1     70         A        30       L                                        3-2     70         A        30       N                                        4       50         A        50       K                                        5-1     40         A        60       K                                        5-2     40         A        60       L                                        ______________________________________                                         *See Table 1B for the identities.                                        

                  TABLE 1B                                                        ______________________________________                                        Identities of Table 1A Solids Materials                                       ______________________________________                                        Epoxy Resin                                                                   Code for                                                                      Epoxy Resin                Estimated Approx.                                  Component                                                                              Composition       Mol. Wt.                                           ______________________________________                                        A        Dow DER-333        9,000                                                      epoxy resin advanced                                                                            (manufacturer's                                             with bisphenol A  figure)                                                     (65/35)                                                              B        liquid epoxy       5,000 (approx.)                                            resin advanced with                                                                             (oxirane                                                    bisphenol A       termination)                                       ______________________________________                                        Extender Polymer                                                              Code for                                                                      Extender                                                                      Polymer                                                                       Component                                                                              Composition       Approx. Mol. Wt.                                   ______________________________________                                        K        polystyrene       15,000 (approx.)                                   L        polybutene 24       950                                                       (Chevron Chemical Co.)                                               N        Cumar-R-1           730                                                       (Coumarone-indene polymer                                                     from Neville Chemical Co.)                                           O        epoxidized polybutadiene                                                                        700-800                                            ______________________________________                                    

Step Three The Grafting Reaction: A, General

Enough solvent is employed to facilitate handling. The amount and kindof monomer to be employed will depend upon several factors. Theseinclude the proportions and identities of the epoxy resin and of theextender polymer in the grafting base, and the proportion andionizability of the monomer to be added by the subsequent in situ vinylpolymerization step. Typical amounts of monomer to be added in thisgrafting step would be in the range from 5% to 50% by weight of thegrafting base.

Any free radical source capable of hydrogen abstraction may be used as acatalyst (initiator). The preferred initiator is benzoyl peroxide. It iseffective when used a concentration of at least 3% by weight of themonomer and at a temperature of about 100° C. to generally not above130° C. Preferably the concentration is above about 4% based on monomer,and the temperature is in the range from 110° C. to 120° C. Mostpreferably, the concentration of benzoyl peroxide is from 6% to 7% basedon monomer. Mixtures of peroxide-type initiators may also be used.

When the epoxy resin has been terminated, with the elimination ofsubstantially all of the epoxy groups, there is no danger of anesterification reaction occurring between the epoxy resin and anyethylenically unsaturated carboxylic acid in the monomer component, orany acid decomposition product from the initiator. Accordingly, higherreaction temperatures may be employed for the grafting-additionpolymerization reaction, and a wider variety of initiators may beemployed, requiring or permitting the use of a much broader range ofreaction temperatures. For example, dicumyl peroxide can be used atreaction temperatures of about 140° C. to 160° C., or even higher.

Examples of other initiators are alkyl peroxy esters, alkyl peroxides,alkyl hydroperoxides, diacyl peroxides, t-butyl perbenzoate, lauroylperoxide, dicumyl peroxide, decanoyl peroxide, and caproyl peroxide.

The term "graft polymer resinous reaction product" and the briefer"resinous reaction product" are used to refer to the reaction mixturethat is produced by this step. The epoxy resin and extender polymerpreferably each have aliphatic backbone carbons having one or twohydrogens bonded thereto in the ungrafted state. In the presence of atleast 3% benzoyl peroxide (BPO) or equivalent hydrogen-extractinginitiator, based on monomer, the monomer is polymerized andsimultaneously grafted at one or more of these backbone carbons, on theepoxy resin and, it is believed, on the extender polymer as well.

The resinous reaction product is believed to be properly characterizedas a mixture of unreacted epoxy resin, unreacted extender polymer, andthree other associatively-formed polymers. One of theseassociatively-formed polymers is the epoxy-based graft polymer. Asecond, Graft polymer is believed to be formed on the extender polymer.The third associatively-formed polymer is ungrafted addition copolymer.

The grafting reaction has several important results: an increase in thesolids content of the mixture, with a relatively low cost material; amodification of the characteristics of the components of the graftingbase, by the introduction of a different component that influencesproduct characteristics in a desirable way, particularly with respect tohydrolytic stability, and weathering and mechanical properties; anincrease in the compatability of those residual reactants present thatare not grafted and that are otherwise mutually incompatible, in thesolid state. This last point is particularly important with respect tounpigmented films formed from the products of this step, where clarityand transparency are important and where the presence of incompatiblephases would lead to haziness or worse.

Another important result of the grafting reaction is the introduction ofsites that are ionizable. The ionizable sites may be either anionic orcationic, depending upon the nature of the monomer component. Forsanitary coating applications, they are anionic.

A concomitant result is that those sites along the backbones in thegrafting base, that are most susceptible to attack, are preempted andoccupied thus improving the resistance of the product to chemicalattack.

Since the grafting reaction is effected by carbon-to-carbon bonding, thegraft polymers produced are not susceptible to hydrolysis.

The Grafting Reaction: B, Acid-Functional Resinous Reaction Products

The vinyl monomer may be a single monomer but preferably is a monomermixture. To make an acid-functional product, ethylenically unsaturatedacids, particularly acrylic acid and methacrylic acid, are preferredcomponents. Styrene is a valuable monomer for use because it iseconomical and has other desirable properties. Ethylenically unsaturatedacid esters are also useful, such as, for example, ethyl acrylate, butylacrylate, the corresponding esters of methacrylic acid, and the like.

The ethylenically unsaturated acids include true acrylic acid and loweralkyl substituted acrylic acids, that is, those acids having ethylenicunsaturation in a position that is alpha, beta, to a single carboxylicacid group. The preferred acrylic acid is methacrylic acid.

The monomer component will preferably contain a major proportion of anacrylic acid, preferably methacrylic acid. When a styrenic monomer suchas styrene is employed, it constitutes, ordinarily, a minor portion ofthe monomer component. For those coating compositions that may come incontact with food, and for the preparation of beverage can coatingcompositions in particular, one preferred addition polymerizable monomermixture is made from 70 parts by weight of methacrylic acid to 30 partsby weight of styrene to 1 part by weight of ethyl acrylate. Anotherpreferred monomer mixture includes methacrylic acid, styrene, and ethylacrylate, in the approximate weight ratio of 65:34:1 respectively.

The Grafting Reaction: C, Base-Functional Products

Base-functional resinous reaction products may be made by incorporatingan amine in the graft polymer molecule. There are two preferred ways todo this.

First, an unsaturated amine, such as dimethylaminoethyl methacrylate ort-butyl amino ethyl methacrylate, is employed in the monomer mixturethat is used to form the graft polymer resinous reaction product. Inthis case, the balance of the monomer mixture comprises monomermaterials such as styrene, lower alkyl acrylates, hydroxyethyl acrylate,and the like.

Second, a material such as glycidyl methacrylate is included in amonomer mixture that does not include other functional monomers. Thisintroduces epoxy groups into the side chains of the graft polymerproduct, and these can be reacted with primary or secondary amines, tomake the graft polymer (and ungrafted addition copolymer) basefunctional.

In addition, if the ungrafted epoxy resin and the epoxy resin componentof the graft polymer have terminal epoxy groups available for reaction,they may be reacted with primary or secondary amines, to impart somebase functionality.

The Grafting Reaction: D, The Resinous Reaction Product

The solids produced by the grafting reaction should contain a sufficientnumber of ionizable sites so that when added to an aqueous mediumcontaining an ionizing agent, the solids become established as adispersion in the aqueous medium. The dispersibility or solubility ofthe product depends upon the strength and degree of ionization. Thedispersibility should be at least sufficient that the entire resinousreaction product is readily dispersed in the aqueous vehicle in whichionization occurs.

Generally, where carboxylic acid monomer units are responsible for acidfunctionality, these units should constitute at least 5% by weight ofthe resinous reaction product of the grafting reaction, and preferably,at least about 10% or so. It is best to combine the weight percent ofcarboxylic acid units with a measurement of the Acid Number value forthe resinous reaction product, based on non-volatiles (N.V.). Also,since some carboxylic acid units may be consumed during a graftingreaction, as by ester formation with epoxide groups, a second measure ofacid functionality, such as Acid Number (N.V.), provides a betterindication of ionizing potential. Generally, the Acid Number of theresinous reaction product of the grafting reaction should be in therange from 30 to 220, and preferably from 45 to 150.

In the case where the resinous reaction product of the grafting reactionis base-functional, a convenient indicator of ionizable potential is thetertiary amine nitrogen content, or the equivalent and the useful rangeis from about 0.1% tertiary amino nitrogen to about 5% tertiary aminonitrogen. A secondary amine nitrogen can be ionized, but has lesseffect. A tertiary amino nitrogen can be ionized by an acid, such ashydrochloric, lactic, or acetic acid, or by a quaternizing agent such asdimethyl sulfate. When the ionization is derived from quaternarynitrogen, a lower nitrogen content is needed for the same result than isthe case where the ionization is derived from tertiary amine nitrogen.

SECOND PREFERRED EMBODIMENT Steps 1, 2, and 3 The Grafting Base, and theGrafting Reaction

In the second preferred process for preparing a grafting base, theextender polymer contains ethylenic unsaturation. Polybutadiene is thepreferred material in this category.

The ethylenic unsaturation offers a site at which side chains can attachduring the addition polymerization-grafting step, in place of or inaddition to grafting to the epoxy resin backbone. Similarly, furtherhomopolymerization, or copolymerization with the addition polymerizablemonomer, may occur, Also, all of these may occur at the same time. Infact, all of these possible addition polymerization reactions appear tooccur, simultaneously with grafting to the epoxy resin. The limitedevidence that is available indicates that all of these reactions dooccur at once, especially where relatively high (25%) amounts of theextender polymer are present, and that simultaneously, grafting takesplace by the attachment of side chains on the epoxy resin backbone, justas though the extender polymer were not present. That such grafting doesoccur is demonstrated by the stability of the aqueous dispersions thatare obtained in the next step, and by the fact that films cast fromeither solutions or dispersions of the resinous reaction products areclear and free from haze.

Except for the composition of the grafting base, and subject to theabove, the grafting reaction and the dispersion and in situ vinylpolymerization steps (Steps 4 and 5) are substantially the same.

Some representative grafting base compositions are described in Table 2below.

                  TABLE 2                                                         ______________________________________                                        Representative Grafting Base Solids Compositions                              Second Preferred Embodiment                                                                           Extender                                              Grafting                                                                             Epoxy Resin Component                                                                          Polymer Component                                     Base   % by Weight          % by Weight                                       Nos.   Based on Solids                                                                           Identity Based on Solids                                                                         Identity*                               ______________________________________                                        6-1    85          B*       15        M**                                     6-2    70          A*       30        M                                       ______________________________________                                         *See Table 1B above                                                           **M is polybutadiene (Lithene P.sub.1, Rivertex Corp.) with an approximat     molecular weight of 900.                                                 

Step Four Dispersion in an Aqueous Medium

The term "aqueous dispersion" as used herein is intended to encompassboth solutions and dispersions. Solutions generally require a higherdegree of ionization than is practical or needed. This invention isprimarily concerned with true dispersions, which may be defined assuspensions of colloidal or larger particles in an aqueous medium.

To form the resinous reaction product of the grafting reaction into anaqueous dispersion, it is mixed with water containing an ionizing agent.For this reason, the solvents used should be water-miscible.

For an acid-functional product, a fugitive base is used as the ionizingagent. For a base-functional product, the ionizing agent may be afugitive acid, such as acetic acid. A fugitive ionizing agent is onethat volatilizes at the curing temperature for the product, leaving noappreciable residue.

To convert a reaction mixture to an aqueous suspensions, the techniquesemployed are essentially conventional. An acid functional resinousreaction product is dispersed in deionized water using a base such as aprimary, secondary, and tertiary alkyl, alkanol, or aromatic amine oralkanolalkyl mixed amine; e.g. mono-ethanol amine, dimethyl ethanolamine, diethanol amine, triethyl amine, dimethyl aniline, ammoniumhydroxide, or the like. Ordinarily this is done by adding the amine tosome water, and then mixing the resinous reaction product with thewater.

The ease with which the dispersion will form will depend upon the numberof ionized sites and the strength and degree of ionization. In somecases, agitation may be required to establish the dispersion, althoughpreferably, the strength and degree of ionization will suffice so that adispersion is easily established and maintained.

For water reducible protective and decorative coating compositions forgeneral applications, there is great flexibility in formulation. Somerepresentative compositions are described below in Table 2, in which thecomposition of the grafting base solids is not specified, but may be asdescribed above.

                  TABLE 3                                                         ______________________________________                                        Step Three Products: Representative Dispersion Compositions                   Component     Parts by Weight                                                 ______________________________________                                        grafting base 95      75     60   37.5  12.5                                  addition polymerizable                                                                      5       25     40   62.5  87.5                                  monomer including an                                                          acrylic acid                                                                  2-butoxy-ethanol-1                                                                          30.4    24     24   24    24                                    n-butanol     45.6    36     36   36    36                                    dimethyl ethanol                                                                            7.6      6      6   6     6                                     amine                                                                         (ionizing agent)                                                              demineralized water                                                                         310     245    245  245   245                                   Total         493.6   411    411  411   411                                   ______________________________________                                    

The Table 2 compositions describe dispersions of neutralized, ionized,acid-functional graft polymer resinous reaction products.Base-functional resinous reaction products can be made in similarfashion, by substituting an unsaturated amine for the unsaturated acidin the monomer, during the grafting step, and by using an acid or aquaternizing agent, or a mixture of these, for ionization.

To make a dispersion useful in the preparation of a sprayable cancoating composition from a Step 4 product, the film-forming resinoussolids should be derived from an initial reactant epoxy resin in anamount of at least about 50% by weight of the solids, and preferablyabout 60%, and the epoxy resin should have an EEW of at least 2,000. Interms of the grafting base, the grafting base could contain, forexample, at least about 60% by weight of solids derived from orcontributed by the epoxy resin based on total solids; the epoxy resinshould have an EEW of at least 2,000 (and a molecular weight of at least4,000); and the grafting base should contribute at least about 78% byweight of the solids present in the final product.

For example, if the can coating is to be based on at least 40% epoxy,which is considered the minimum level for producing acceptableproperties, then if the grafting base is to contribute 80% of the solidsof the coating, it must initially contain 50% by weight of epoxy resin.Similarly, if the can coating is to be based on at least 45% epoxy, amore preferred level, then the grafting base must initially containabout 56% by weight of epoxy resin.

Step Five Vinyl Polymerizaton In Situ

Additional monomer is added to the dispersion produced by the previoussteps, together with additional initiator, and the temperature is thenraised to a suitable reaction temperature while the mixture is agitated,to cause in situ polymerization of the added monomer to occur. Generallymore deionized water is also added.

Since the end product of this step is an aqueous dispersion containingadded solids, the extent and degree or strength of ionization alreadypresent in the dispersion will be important factors in determining boththe amount and the identity of the monomer component employed in thisfifth step. Thus, if sufficient ionization is present to establish andmaintain dispersed the solids to be added, then there need not beadditional ionizable sites added, and the monomer component may be amaterial such as styrene, selected for the properties that it willimpart and for its economy. On the other hand, if additional ionizablesites must be introduced, then the monomer component will be selectedaccordingly.

Additional demineralized water may also be added, so that the materialhas the requisite characteristics for the kind of application intended.For example, for spraying, a solids content of about 19%-22% by weightis a preferred useful range to employ, although the broader solidsconcentration of from 10% to 30% by weight is useful. For applicationtechniques other than spraying, a solids content in the range from about10% to about 40% or even more is useful. While the use of an aminoplastcross-linker is convenient, the products produced by the presentinvention are self-cross-linking with heat to a limited extent, ifterminal epoxy groups are present.

The dispersions that are produced in accordance with the presentinvention are generally useful as film-forming, surface coatingmaterials, the preferred application being in the formulation ofsprayable compositions for coating beverage cans.

The chemical system present in the dispersion products of the presentinvention is a rather complicated one. Indications are that after the insitu vinyl polymerization of step five, some additional grafting mayoccur, when the initiator is one that abstracts hydrogen. Complete,accurate characterization of the solids present will require a good dealof work, due to the complexity of the processes and the ingredients.

There are many advantages to modifying the dispersed reaction product ofthe fourth step by supplementing its solids content through the in situvinyl polymerization. One obvious advantage is economy, since generally,the material that is added is less expensive than the epoxy component.In addition, the amount of organic solvent as a percentage of the finalproduct is substantially reduced, through the addition of more solidsand more water. Another important advantage is that the in situpolymerization can be carried out in the same reaction vessel in whichthe graft polymer-containing resinous reaction product is produced, andtherefore does not require additional equipment, and in fact, makes moreefficient use of existing equipment.

Based upon 100 parts of resinous reaction product solids as input forthe in situ polymerization, about 10 parts to 225 parts of added vinylmonomer represents a feasible range of addition. However, a greateramount may be added if desired, if appropriate steps are taken tocompensate for the changed characteristics of the product, having inmind the intended end use. On the other hand, there is little point ingoing through this step unless a significant amount of monomer is addedto the solids already present. While a practical minimum is about 10parts of added monomer for each 100 parts of input solids, as little canbe added as desired. One presently preferred practical range of additionis from about 12 parts to about 70 parts added per 100 parts of inputresinous reaction product solids, for most coating compositions.

In practice, a sufficient amount of monomer is added so that the solidsadded contribute from about 10% to about 40% and preferably, aboutone-third of the total solids in the final product. This can often offera material advantage in respect of economic considerations withoutsubstantial loss in functional properties, for example for sanitary(can) coatings produced in accordance with one preferred embodiment ofthe invention, as hereafter described.

For can coatings the amount of solids added at this stage will tend tobe governed by a balance of properties against cost. For goodproperties, the epoxy resin should contribute at least 30% of totalsolids, preferably 40%, and more preferably, about 45% to 50%, and thisfactor, together with the amount and nature of other solids alreadypresent, governs what and how much can be added in this step.

In a variation, the resinous reaction product containing the graftpolymers may be prepared utilizing an amine, so that the graft polymersand, depending on the process employed, the ungrafted addition polymeralso, may be base-functional. In this case, dispersion in water isaccomplished by the addition of an agent that ionizes the amine groups.The resulting dispersion is then useful for the in situ vinylpolymerization step, and in this case, the added monomer should produceeither nonionic products or base-functional products.

Useful vinyl monomers for this step include vinylidene chloride;arylalkenes, such as styrene, vinyl toluene, alpha-methyl styrene,dichlorostyrene, and the like; C-1 to C-15 alkyl acrylate esters, andparticularly, lower alkyl acrylates, such as methyl acrylate, butylacrylate, and lower alkyl methacrylates, such as methyl methacrylate,butyl methacrylate, and, as well, the nonyl, decyl, lauryl, isobornyl,2-ethyl hexyl, and octyl esters of acrylic or methacrylic acid, alsotrimethylol-propane trimethacrylat 1,6-hexanediol dimethacrylate, andthe like; hydroxy lower alkyl acrylates, such as hydroxy propylacrylate, hydroxy ethyl acrylate, and the like; hydroxy lower alkylmethacrylates, such as hydroxy ethyl methacrylate, hydroxy propylmethacrylate, and the like; lower alkenyl carboxylic acids, such asacrylic acid, methacrylic acid, and the like; lower alkenyl amide, suchas acrylamide, methacrylamide, isobutoxymethylacrylamide, and the like;lower hydroxyalkyl alkenyl amides such as hydroxy methyl acrylamide, andthe like; lower alkyl butenedioates such as dibutyl maleate, dibutylfumarate, and the like; vinyl lower alkenoates, such as vinyl acetate,and vinyl propionate, and the like; and mixtures of these.

Presently preferred vinyl monomers include styrene, butyl or ethylacrylate, and methacrylic acid, admixed, with a very small proportionpresent of the acrylate ester. Up to about 25% allyl materials by weightof total vinyl monomer may be included.

In order to cause the vinyl monomer to polymerize, at least oneinitiator is introduced into the aqueous dispersion before or duringaddition thereto, with agitation, of the vinyl monomer. As used herein,the term "initiator" or "free radical initiator" has reference to anysubstance which when added appears to promote addition polymerization.The amount of initiator used typically is in the range from about 0.1 to5 parts per 100 parts by weight of total vinyl monomer added, andpreferably from about 0.5 to 3 parts per 100 parts total vinyl monomer,but larger or smaller amounts may be used.

Initiation provided by a redox system is extremely effective. An organicperoxide may be used or an inorganic peroxide such as hydrogen peroxide,ammonium persulfate, sodium persulfate, or potassium persulfate. Theperoxide catalyst is effectively coupled with a reducing agent such asan alkali metal sulfite, bisulfite, or metabisulfite, or hydrosulfite,or hydrazine. The action of the redox system may be controlled throughthe use of a chain transfer agent or regulator, such as mercaptoethanolor other mercaptan. Such a regulator also finds use outside of redoxsystems with organic or inorganic peroxides and with azo catalysts, suchas azodiisobutyronitrile, azodiisobutyramide, or diethylazodiisobutyrate. Examples of other suitable azo catalysts includedimethyl or dibutyl azodiisobutyrate, azobis(α,γ-dimethylvaleronitrile), azobis (α-methylbutyronitrile), azobis(α-methylvaleronitrile), dimethyl or diethyl azobismethylvalerate, andthe like.

Preferred such initiators comprise the persulfates, such as potassiumpersulfate, sodium persulfate, ammonium persulfate, and the like.Another useful class of initiators comprises percarbonates, such asdiisopropyl percarbonate, and the like.

Another useful but less preferred class of initiators for this in situpolymerization comprises organic peroxides. One group of suitableperoxides comprises diacyl peroxides, such as benzoyl peroxide, lauroylperoxide, acetyl peroxide, caproyl peroxide, butyl perbenzoate,2,4-dichloro benzoyl peroxide, p-chlorobenzoyl peroxide, and the like.Another group comprises ketone proxides, such as methyl ethyl ketoneperoxide and the like. Another group comprises alkyl hydroperoxides suchas t-butyl hydroperoxide, and the like. Another group comprises aqueoushydrogen peroxides.

Generally, the initiator is chosen with a half life such that aneffective amount is present during the polymerization to insure completereaction. The preferred initiators are those which are virtuallycompletely consumed when the polymerization is complete.

Certain other classes of materials can be present at the time of, orduring such a polymerization, such as chain transfer agents such asn-octylmercaptan, and t-dodecyl mercaptan; reducing agents, such assodium bisulfite, sodium formaldehyde sulfoxylate, sodium hydrosulfite,and sodium thiosulfate, and the like agents. The amount of such agentsor additives if such as used is characteristically less than about fiveweight percent based on total solids present in a reaction system. Suchadditives are known to those skilled in the art of vinyl monomerpolymerization.

In general, in situ polymerization of the vinyl monomer in accordancewith the teachings of this invention permits wide flexibility as to thekinds of initiator employed and the reaction temperature. It generallyproceeds under liquid phase conditions at temperatures in the range fromabout 25° C. to 100° C., and preferably from 50° C. to 100° C., and mostpreferably, from about 50° C. to 80° C. When the extender polymeremployed exhibits a tendency to gel, those higher temperatures thatmight favor gelation should be avoided.

Under some circumstances, the use of exceptionally high temperatures maybe desired. In such cases, when the epoxy resin has been terminated toreduce the liklihood of desired reactions, the polymerizationtemperature may be as high as 160° C. The rate of monomer polymerizationis controlled not only by temperature, but also by such variables as theamount and type of initiator(s) used, initiator concentration, theconcentration and type of other solids present, and by other factors.

The vinyl monomer generally is added gradually or by increments to anaqueous dispersion of the resinous reaction product at a rate such thatthe exothermic polymerization can be controlled adequately. Underfavorable circumstances, such as controllable exotherm, the monomer canbe added in bulk, and this technique is generally preferred for theproduction of dispersions to be used in formulating sanitary coatingcompositions. However, some of the monomer may be present with thedispersion as a "heel", at the time the remainder of the monomer, plusinitiator, is added.

The solids are already dispersed, and any further ionization desiredproceeds generally as in Step 4. Thus, for ionizing an in situacid-functional vinyl polymerizate (and any nonionized but ionizablesites already present in the dispersion), dimethyl ethanolamine is apreferred fugitive ionizing agent. Other fugitive bases that may beemployed include di-isopropanolamine, triethanolamine,triisopropanolamine, diethyl ethanolamine, and ammonia.

When the ionizable solids are base-functional, the neutralizing agentemployed is an acid, preferably a fugitive acid. A few representativesuitable materials are hydrochloric acid, sulfuric acid, phosphoricacid, formic acid, chloroacetic acid, acetic acid, glycolic acid, malicacid, maleic acid, fumaric acid, succinic acid, lactic acid, and thelike. Quaternizing agents may also be employed in connection withtertiary amino nitrogens in the molecule. These may include, forexample, methyl iodide, dimethyl sulfate, methyl chloride, ethylchloride, and the like.

For coatings that will be in contact with edibles, toxic materialsshould be avoided.

The product of this fifth step is a dispersion that contains a highproportion of ionized, film-forming, polymeric material. The ionizedmaterial consists of the ionized graft polymers, and the ionizedungrafted addition polymer present. The solids in the product arepresent as an ultrafine dispersion of very fine solid particles in theaqueous vehicle, with the sizes of the particles distributed over abroad range.

If in the third step, a grafting base containing 40 parts of epoxy resinand 40 parts of polystyrene, in solution, is reacted with 20 parts of amonomer mixture consisting of a major amount of methacrylic acid andminor amount of styrene, reacted at about 115° C. to 120° C. and in thepresence of about 6.7% BPO, dry basis, then an acid functional resinousreaction product may be obtained that contains a substantial amount ofgraft polymer, together with ungrafted, ionizable addition polymer, andunreacted grafting base solids comprising unreacted epoxy resin andunreacted extender polymer. If then, 15 to 50 parts of ethylenicallyunsaturated monomer, such as styrene or styrene plus methacrylic acidand/or ethyl acrylate, are subjected to addition polymerizationconditions in the presence of 75 parts by weight of an aqueousdispersion at 22.5% N.V. of this acid functional resinous reactionproduct, the added ethylenically unsaturated monomer adds to the contentof polymer solids present, while much of the functionality of theoriginal dispersion is preserved. The dispersion that would be producedfrom such an in situ vinyl polymerization would contain about 13.5 partsby weight of solids derived from the grafting base solids, about 3.4parts of solids derived from the grafting step, and 15 to 50 parts ofsolids derived from the in situ polymerized ethylenically unsaturatedmonomer material. Such an aqueous dispersion would be useful in theformulation of wood coatings, clear or pigmented, and could beformulated for any type of application desired, i.e., brushing, rolling,spraying, and the like.

Wide variations in composition are of course possible, for other typesof formulations intended for the same or other purposes. Some of thepossibilities are summarized briefly in the tabular presentations inTables 4 and 5 below. In Table 4, it is assumed that 10 parts of solidsare added by the in situ vinyl polymerization step.

                  TABLE 4                                                         ______________________________________                                        Representative Product Compositions (By Weight,                               Dry Solids Basis), 10 Parts of Solids Added In The                            in situ Vinyl Polymerization                                                  Component                                                                     Providing                                                                     Source                                                                        of Solids                                                                              Parts  %      Parts                                                                              %    Parts                                                                              %    Parts                                                                              %                             ______________________________________                                        Grafting Base                                                                          95     86.4   80   72.7 50   45.5 30   27.3                          Third Step                                                                              5     4.5    20   18.2 50   45.5 70   73.6                          Addition                                                                      Polymeriz-                                                                    able                                                                          Monomer                                                                       Fifth Step In                                                                          10     9.1    10    9.1 10    9.1 10    9.1                          Situ Vinyl                                                                    Polymeri-                                                                     zation                                                                        Total    110    100    110  100  110  100  110  100                           ______________________________________                                    

In Table 5, it is assumed that the added in situ polymerization adds 40%by weight to the solids content of the dispersion.

                  TABLE 5                                                         ______________________________________                                        Representative Product Compositions (By Weight                                Dry, Solids Basis) 40% Solids Added by the                                    In Situ Vinyl Polymerization                                                  Component                                                                     Providing                                                                     Source of                                                                     Solids   Parts  %      Parts                                                                              %    Parts                                                                              %    Parts                                                                              %                             ______________________________________                                        Grafting 95     57     80   48   50   30   30   18                            Base                                                                          Third     5      3     20   12   50   30   70   42                            Step                                                                          Addition                                                                      Polymeriza-                                                                   tion                                                                          Monomer                                                                       Fifth    66     40     66   40   66   40   66   40                            Step                                                                          In Situ                                                                       Vinyl                                                                         Polymeriza-                                                                   tion                                                                          Total    166    100    166  100  166  100  166  100                           ______________________________________                                    

In both tables above, the composition of the grafting base is notspecified. It may be selected and adjusted to produce desired finalproduct compositions and properties.

Those compositions having about 40% or more of total solids contributedby the initial epoxy resin component wet and adhere to metal surfaceswell, and form good barrier films. The added addition polymerizablemonomer improves the weathering and other characteristics of film formedfrom the composition. Where economy is important, or for application tosurfaces other than metal, valuable coating compositions can be preparedwith a relatively small contribution from the epoxy resin.

For ease in handling, and for application properties, water may be addedduring the in situ reaction, so that while the solids are increased bythis step in total amount, the solids concentration may remainsubstantially constant. Obviously, changes in the amount, proportions,or nature of the materials employed in this step will affect thecomposition and properties of the final product.

For general types of applications including spraying, the aqueousdispersion may comprise, preferably, from about 10% to 40% solids, whichare proportioned as follows: about 0.1% to about 16% by weight of across-linking agent, and about 6% to about 39.9% by weight of the solidsfrom a reaction mixture produced in accordance with the presentinvention; and about 60% to about 90% volatile components, generallydivided into about 6% to about 35% organic solvent, and about 25% toabout 80% water. It is preferred but not essential that some organicsolvent be used to facilitate application, and it is generally used inthe ratio of one part by weight of solvent to about three parts byweight of water.

The resulting aqueous coating composition can be applied satisfactorilyby any conventional method known in the coating industry. Thus,spraying, rolling, dipping, flow coating or electrodepositionapplications can be used for both clear and pigmented films. Oftenspraying is preferred. After application onto a metal substrate, thecoating is cured thermally at temperatures in the range from about 95°C. to about 235° C. or higher, for periods in the range from about 1 toabout 20 minutes, such time being sufficient to effect curing as well asvolatilization of any fugitive component therein. Further, films may beair dried at ambient temperatures for longer periods of time.

If desired, some or even all of the organic solvent present can becompletely removed prior to final formulation, by vacuum evaporation(distillation) at a moderate temperature. If this is done, the solventcontent of the final product may be as low as is desired, includingzero. This can be done for can coating dispersions or for otherapplications if desired. If it is to be done, the solvents selected foruse in the process must have boiling points below that of water.

Sprayable Coating Compositions

Since sprayable compositions are preferred and important embodiments ofthe invention, they are treated separately in this section.

The amount of water in the final product dispersion depends on theviscosity desired, which, in turn, is related to the intended method ofapplication. For spraying, water amounting to about 60% by weight of thedispersion represents a typical level, within a preferred range ofcomposition for the dispersion of from 10% to 30% by weight of solidsand from about 70% to 90% of volatiles, that is, fugitive base, water,and solvents. The fugitive base is usually about from 2% to 6%, waterfrom about 30% to 90% and the organic solvents from about 5% to about40%, all percentages being by weight based on the sprayable dispersion.The solids comprise about 9% to 29% of the reaction mixture solids, andabout 1% to 10% of a crosslinking agent, based on the sprayabledispersion.

The organic solvent can be made up of one or more of the known solventssuch as butanol (normal), 2-butoxy-ethanol-1, xylene, toluene, and othersolvents. It is preferred to use n-butanol in combination with2-butoxy-ethanol-1, in approximately equal amounts. A representativeOS/S ratio for a sprayable can coating is about 0.5.

An aminoplast resin is preferred for use as the cross-linking agent. Itcan be added before any final diluting, or thereafter. Typicalaminoplasts include melamine, benzoguanamine, acetoguanamine, and urearesins such as urea formaldehyde. Commercially available aminoplastswhich are water soluble or water dispersible and useful for the instantpurpose include Cymel 301, Cymel 303, Cymel 370, and Cymel 373 (allbeing products of American Cyanamid, Stamford, Conn., said aminoplastsbeing melamine based, e.g., hexamethoxymethyl melamine for Cymel 301),and Beetle 80 aminoplasts (products of American Cyanamid which aremethylated or butylated ureas.)

Other suitable aminoplast resins are of the type produced by thereaction of aldehyde and formoguanamine; ammeline;2-chloro-4,6-diamine-1,3,5-triazine;2-phenyl-p-oxy-4,6-diamino-1,3,5-triazine; and2,4,6-triethyl-triamino-1,3,5-triazine. The mono-, di-, or triarylmelamines, such as 2,4,6-triphenyl-triamino-1,3,5-triazine, arepreferred. Other aldehydes used to react with the amino compound to formthe resinous material are crotonic aldehyde, acrolein, or compoundswhich generate aldehydes, such as hexamethylene-tetramine, paraldehyde,and the like.

If there is little or no oxirane functionality in the final product,then a cross-linker is necessary; otherwise, it is desirable but theproduct is self cross-linking to some extent with heat.

Another way to introduce cross-linking capability into the reactionmixture and the graft polymer is by utilizing as all or part of thepolymerizable monomer, in the initial reaction mixture, a material suchas acrylamide or an alkyl derivative thereof, or a material such as bismaleimide.

The coating composition of the present invention can be pigmented and/oropacified with known pigments and opacifiers. For many uses, includingfood uses, the preferred pigment is titanium dioxide. Often the pigmentis used in a pigment-to-binder ratio of 0.1:1 to 1:1, by weight.Titanium dioxide pigment can be incorporated into the composition inamounts in a preferred range of from about 5% to 40% by weight, based onresinous, film-forming solids in the composition. Dyes may also be used,alone or in conjunction with pigment.

For metal sheet substrates intended as beverage containers andparticularly for carbonated beverages such as beer, the coating shouldbe applied at a rate in the range from about 0.5 to about 15 milligramsof binder solids per square inch of exposed metal surface. To attain theforegoing, the water-dispersible coating as applied can be as thick as1/10th mil. to about 1 mil.

Sprayable can coating compositions prepared in accordance with thepresent invention are generally highly resistant to blistering and arewell suited for their intended purpose.

General

The properties of the fifth step product can be substantially customproduced. The strength and degree of ionization in the product can besuch that the particles remain in stable suspension almost indefinitelyunder room temperature storage conditions, without agitation. Theionized material from the reaction product of the third, grafting stepappears to play a role in causing the in situ polymerization to resultin a product in which all of the particles remain dispersed, whetherthey themselves are ionizable or not.

It is possible to employ an external surfactant during the in situpolymerization. The use of an external surfactant appears to be possiblyvaluable for improving the coverage of coatings prepared from the insitu polymerizate. A wide variety of commercially available externalsurfactants is available for use. Anionic agents such as Tamol 731 ofRohm and Haas and Daxad 30 of W. R. Grace are exemplary. Othersatisfactory external surfactants include Aerosol MA, a product ofAmerican Cyanamid, available as an 80% solution in water to tetra sodiumN-(1,2-dicarboxyethyl-N-octadecyl-sulfosuccinamate), and Aerosol 22,another product of American Cyanamid, available as a 35% solution inwater of sodium dihexyl sulfosuccinate. Combinations of two or moreexternal surfactants may also be used.

The introduction of a wetting agent as an external surfactant may affectblush resistance, particularly at baking temperatures below 375° F.(191° C.). The addition of a cross-linker such as Cymel 303, however,apparently improves the situation.

The amount of solvent and water present in the fourth (dispersion) stepproduct should be kept at a level that facilitates handling. Preferably,the solvent system used is a water-miscible system. Epoxy resins aregenerally soluble in ketones, ethers, and esters. Solvents that may beused are n-propyl ketone, methyl isobutyl ketone, diisobutyl ether,n-propyl acetate, n-butyl acetate, ethyl butyrate, an alkoxyethanol, oran alkyl ether of diethylene glycol. The preferred solvent is2-butoxy-ethanol-1.

Preferably, in addition to a solvent for the epoxy resin, a secondorganic liquid solvent is present that need not necessarily dissolve theepoxy resin itself, but that is preferably miscible with the firstsolvent, and that preferably can dissolve or solvate the side chains onthe backbone resin in the graft polymer and the addition polymer, thatis associatively formed with the graft polymer, in the third step aswell. The preferred second solvent is n-butanol.

One very important purpose of the solvent(s) is to facilitate handlingduring the several process steps. The extender polymer preferably isselected for solubility in the solvent system used.

From the standpoints of ease of handling, and workability, a 40%concentration of solids in any product may be workable, depending on itsconstitution, but a product at even 35% solids is very thick.Accordingly, it will often be found convenient to produce product at 20%to 30% solids content. The preferred dispersions are opalescent inappearance.

The epoxy resins employed in the practice of the invention have beenidentified primarily in terms of desired molecular weight and/or EEW.They are more specifically identified in the earlier applicationsmentioned above. Dow Chemical's D.E.R. 331 epoxy resin is a preferredlow molecular weight starting resin, but its EEW is preferably advancedto about 4,000 or so for use. Comparable, commercially available epoxyresins can be advanced to a useful EEW with a catalyst such as sodium orpotassium acetate or similar alkaline material. Since some resins aresold in solvents and/or with residual catalysts, care must be exercised.

Dow's D.E.R. 669 epoxy resin, EEW about 4,500, is useful, as is itsD.E.R. 668, EEW about 2,750. Shell's Epon Resin 1010, EEW about 5,000,and its Epon Resin 1009, EEW about 3,250, are also useful; these aresolid resins.

The invention will now be further explained by several demonstrations ofits practice. Throughout this application and especially in thefollowing examples, all parts and percentages are by weight, and alltemperatures are in °C., unless expressly stated to be otherwise. Theepoxy resin molecular weights referred to hereafter are those calculatedfrom end group analysis data.

The first five examples describe the production of grafting base.

GRAFTING BASE PRODUCTION Example 1 Grafting Base: Epoxy Resin WithPolystyrene

The polystyrene extender polymer was first formed as follows: 283 gms.of 2-butoxyethanol-1 was charged into a 5 liter round bottom flask whichwas fitted with a water-cooled condenser, nitrogen inlet, a stirrer, anda thermometer, heated by an electric heating mantle. The2-butoxyethanol-1 was heated to about 110° C. and to this heated solventsolution was gradually added a monomer mixture composed of 74 gms. ofstyrene and 4 gms. of benzoyl peroxide (BPO, 78% in H2O). The additionof monomer took 2 hours then a shot of chaser of 1.4 gms. of BPO (78%)in 10 gms. of 2-butoxyethanol-1 was added to the reaction mixture. Afterthe addition of the chaser, the addition mixture was held for 1/2 hourand the chaser step was repeated. After the 2nd chaser was added, thepolymerization mixture was held for 2 hours. At the end of that time avacuum was applied to the reaction mixture to remove water.

After the water was removed, 872 gms. of a liquid epoxy resin, DowDER-333, and 470 gms. of bisphenol A were charged into the reactionflask. The temperature fell to 95° C. and heating was continued. Whenthe temperature was at 140° C., heating was turned off and the exothermraised the temperature to 151° C. At that time heating was resumed andthe temperature reached 180° C. in 5 minutes. The temperature was heldat 170° C. for the next 3 hours.

The oxirane value of the reaction mixture was determined at the end ofeach hour during the 3 hour hold period. These oxirane values were 0.3,0.26, and 0.24, respectively. The method used for determining oxiranevalue was that described in the issued patents and publishedapplications identified in the discussion above of related patentapplications. At the end of the 3 hour hold period, 254 gms. of2-butoxyethanol-1 was added, followed by 889 gms. of n-butanol.

The product was a solution of a fluent, filterable mixture of epoxyresin with polystyrene, having the approximate composition of GraftingBase 1-1 of Table 1A above. It is generally useful as a material forgrafting as in Step 3 of the process of this invention, and as will bespecifically described presently.

Example 2 Grafting Base: Epoxy Resin With Polybutene

In this demonstration of grafting base production, the extender polymer,polybutene, is a preformed, commercially available polymer.

1141 gms. of a liquid epoxy resin, Dow DER-333, 614 gms. of bisphenol A,310 gms. of 2-butoxyethanol-1, and 435 gms. of polybutene 24 (fromChevron Chemical Co., California), were charged into a 5 liter roundbottom flask equipped with N₂ inlet, condenser, stirrer and athermometer. The reaction mixture was heated to 140° C., where a smallexotherm occurred. Heating was resumed until the batch temperatureincreased to 175° C. The batch was then held at 175° C. for 3 hours. Theviscosity of the resin was observed at the end of each hour hold,measured in 2-butoxy-ethanol-1 at 40% NV, with the values R, S, and S,respectively. At the end of the third hour hold, 996 gms. of n-butanolwere added to the reaction mixture, and the temperature was thenstabilized to 112° C.

The product was a filterable solution of a mixture of epoxy resin withpolybutene, having approximately the composition of grafting base 2-3 ofTable 1A above. It also is generally useful as a material for grafting,as in Step 3 of the process of this invention.

Example 3 Grafting Base: Epoxy Resin with Epoxidized Polybutadiene

Into a 5-liter round bottom flask equipped with nitrogen inlet,water-cooled condenser, mechanical agitator and a thermometer wascharged 1085 gm. of liquid epoxy resin (Epon 828), 614 gm. of bisphenolA, 57 gm. of xylene, 100 gm. of epoxidized polybutadiene (Mn 700-800,oxirane oxygen content 7.5%), and 310 gm. of 2-butoxy-ethanol-1.

The reaction mixture was heated to 50° C. under a nitrogen sparge, and0.5 gm. of sodium acetate trihydrate in 9 gm. of water was added to thereaction mixture. At that time, the nitrogen was turned off, a vacuum of17" was applied and heating continued.

When the temperature reached 135° C., the vacuum was turned off andreplaced by the nitrogen sparge. 25.5 gm. of liquid was collected. Therewas an exotherm observed at 140°-150° C., and the temperature climbed to180° C., where it was maintained. After 3 hours at that temperature, theviscosity of the batch was X-(the cut was made by taking 10 gm. of thereaction mixture with 11.25 gm. of 2-butoxy-ethanol-1). At that time,heating was discontinued and 1200 gm. of n-butanol was carefully added.

The product was a fluent, filterable mixture of an oxirane-terminatedepoxy resin with epoxidized polybutadiene, having the composition ofGrafting Base 1-4 of Table 1A above. It is generally useful as amaterial for grafting as in Step 3 of the process of this invention, aswill be described presently.

Generally, the extender polymer is one that is substantially inert bothto the epoxy resin and to the polyfunctional advancing agent, under theconditions of advancement. However, as this example demonstrates, it isfeasible to use an extender polymer that is merely of lesser reactivityto the advancing agent than is the epoxy resin, and that issubstantially non-reactive with the epoxy resin itself under theconditions of advancement.

Example 4 Grafting Base: Epoxy Resin with Coumarone-Indene Resin

Into a 5-liter round bottom flask was charged 1085 gm. of liquid epoxyresin (Epon 828), 614 gm. of bisphenol A, 57 gm. of xylene, 300 gm. ofcoumaron-indene resin (Cumar-R-1 from Neville Chemical Co., Mn 730) and421 gm. of 2-butoxy-ethanol-1. The flask was fitted with a water-cooledcondenser, N2 inlet, mechanical stirrer and a thermometer.

The mixture was heated under N2 sparge and at 80° C., a solution of 0.8gm. of sodium acetate in 9 gm. of water was added to the reactionmixture. At that time, a vacuum of 18 inches was applied to the flaskand heating continued. When the temperature reached 140° C., heating wasstopped and the vacuum was turned off. 33 gm. of liquid was collected inthe vacuum trap. There was a slight exotherm as the temperatureincreased to 150° C., at which time heating was resumed. The temperaturewas stabilized at 175° C. for 4 hours. At the end of that time, theviscosity of the reaction mixture was U (viscosity sample prepared at40% NV in 2-butoxy-ethanol-1). Heating was stopped and 1089 gm. ofn-butanol was added.

The product was a fluent and filterable mixture of oxirane-terminatedepoxy resin with coumarone-indene resin, having the composition ofGrafting Base 1-5 of Table 1A above. It is generally useful as a Step 3grafting base.

EXAMPLE 5 Grafting Base: Epoxy Resin with Polybutadiene Resin

Into a 5-liter round bottom flask was charged 1085 gm. of liquid epoxyresin (Epon 828), 614 gm. of bisphenol A, 57 gm. of xylene, 300 gm. ofthe polybutadiene and 421 gm. of 2-butoxy-ethanol-1. The mixture washeated to 80° C. under nitrogen sparge and 0.8 gm. of sodium acetatetrihydrate in 9 gm. of water was added. A vacuum of 20" was then appliedto the reaction mixture and heating continued.

At 140° C., the vacuum was broken off and heating stopped. 41.5 gm. ofliquid was collected in the vacuum trap. Heating was continued, untilthe temperature reached 175° C. At that time the temperature wasstabilized for 3 hours. At the end of that time, the viscosity of theresin mixture was V-(40% NV in 2-butoxy-ethanol-1). 1039 gm. ofn-butanol was then added and temperature was stabilized at 115° C.

The product was a fluent and filterable mixture having the compositionof Grafting Base 6-1 of Table 3 above. It is generally useful as a Step3 grafting base.

The Grafting and Dispersion Steps Example 6 Acid Functional ResinousReaction Product From Grafting Base 1-1

The grafting base of Ex. 1 was utilized. A monomer mixture was made upof:

    ______________________________________                                        Ingredient             Grams                                                  ______________________________________                                        methacrylic acid       299                                                    styrene                95                                                     ethyl acrylate          4                                                     benzoyl peroxide (moist; 78% active)                                                                 35                                                     2-butoxyethanol-1      101                                                    ______________________________________                                    

This mixture was slowly added, over a two hour period, to the graftingbase, while maintaining the temperature at about 118° C. 57 gms. ofn-butanol was then added and the reaction mixture was held at 110° C.for 3 hours.

3,188 grams of the solution thus obtained, a graft polymer-containingresinous reaction product (58.1% N.V., AN 85), was added to a mixture of3,862 grams of deionized (DI) water, 229 grams of 2-butoxyethanol-1, and181 grams of dimethylethanol amine. A dispersion formed with thefollowing characteristics:

NV=25.44% (30 min. @ 400° F.)

Viscosity=100 secs., #4 Ford cup at 25°

AN (acid number)=85.3 on NV

BN (base number)=62.8 on NV

% neutralization=72%

This dispersion is useful in its own right. It can be formulated withpigment and a cross-linker, to make a sprayable can coating composition.It is also useful as a medium for in situ vinyl polymerization, as willbe described presently.

Example 7 Acid Functional Resinous Reaction Product from Grafting Base2-3

The temperature of the grafting base solution of Ex. 2 was adjusted toabout 112° C. A monomer mixture of 283 gms. methacrylic acid, 148 gms.styrene, 4 gms. of ethyl acrylate, 38.5 gms. benzoyl peroxide (BPO 78%in water), and 111 gms. of 2-butoxyethanol-1 was slowly added to thegrafting base. The addition of this monomer mixture took 2 hours. At theend of the monomer addition, 255 gms. of n-butanol was added, and thereaction mixture was then held at 112° C. for 3 hours. At the end of the3 hour hold, the graft polymer resinous reaction product was ready to bedispersed in water. The resin viscosity was then K, as measured bydissolving 1 part of the resin solution in 1 part n-methyl pyrrolidone.

2,752 gms. of the graft polymer solution was slowly dropped into aaqueous mixture composed of 3,971 gms. of deionized water and 135 gms.of dimethyl ethanolamine. The dispersion had much opalescent color, anindication of rather small particle size. The constants for the aqueousdispersion were:

NV=24.4%

AN=73.3

BN=50.1

Viscosity=22 secs. #4 Ford Cup

Organic solvent/solids (OS/S)=0.77

This dispersion product was also useful per se. When formulated with anaminoplast it makes an excellent clear protective coating, particularlyuseful for metal surfaces. It can be cured by air drying but preferablyis cured by baking.

Example 8 Acid-Functional Resinous Reaction Product From Grafting Base1-4

The temperature of the grafting base solution of Ex. 3 was adjusted to110° C. A monomer mixture composed of the following was then dropwiseadded:

    ______________________________________                                        methacrylic acid        283    gm.                                            styrene                 148    gm.                                            ethyl acrylate          4      gm.                                            benzoyl peroxide (78% in H.sub.2 O)                                                                   38.5   gm.                                            n-butanol               111    gm.                                            ______________________________________                                    

The addition took 2 hours, and then 62 gm. of n-butanol was added. Thereaction mixture was then held for 3 hours.

At the end of that time, the Gardner viscosity of the reaction mixture(1 pt. resin, 1 pt. N-methyl pyrrolidone) was I.

2705 gm. of the reaction mixture was slowly dropped into 3411 gm. ofdeionized water and 152 gm. of dimethylethanolamine. The temperature ofthe water was about 50° C. At the end of the drop, the temperature ofthe dispersion rose to 75° C. 560 gm. of deionized water was then addedto the dispersion.

The resulting dispersion had the following characteristics:

NV: 24.2%

OS/S: 0.87 The ratio of epoxy:epoxidized polybutadiene:acrylic was76:4.5:19.5.

Example 9 Acid-Functional Resinous Reaction Product From Grafting Base1-5

The temperature of the grafting base reaction mixture of Ex. 4 wasstabilized at 112° C. A monomer mixture was prepared from the following:

    ______________________________________                                        methacrylic acid        283    gm.                                            styrene                 148    gm.                                            ethyl acrylate          4      gm.                                            benzoyl peroxide (78% in H.sub.2 O)                                                                   38.5   gm.                                            n-butanol               111    gm.                                            ______________________________________                                    

This mixture was added slowly to the grafting base over a period of 2hours while keeping the temperature at least as high as 112° C. Afterthen adding 63 gm. of n-butanol, the reaction mixture was held at 110°C. for 3 hours.

A stainless steel vessel was then loaded with 3,411 gm. of deionized(DI) water and 152 gm. of dimethyl ethanolamine. Then 2,711 gm. of thereaction mixture was slowly dropped into the vessel, while mixing with ahigh lift mechanical agitator. A dispersion formed easily. At the end ofthe drop, 560 gm. of deionized water was added.

The constants for the dispersion are:

NV: 24.6%

OS/S: 0.8

The ratio of epoxy:Cumar-R-1:acrylic was 70:12:18. The ratio ofbutanol:2-butoxy-ethanol-1 was 75:25.

Example 10 Acid-Functional Resinous Reaction Product From Grafting Base2-1

A monomer mix was prepared from the following:

    ______________________________________                                        methacrylic acid        283    gm.                                            styrene                 148    gm.                                            ethyl acrylate          4      gm.                                            benzoyl peroxide (78% in water)                                                                       38.5   gm.                                            n-butanol               111    gm.                                            ______________________________________                                    

While the grafting base 2-1 from Ex. 5 was maintained at about 115° C.,the monomer mix was slowly added over a 2 hour period. At the end of themonomer addition, 63 gm. of n-butanol was added and the reaction mixturewas held for 3 hours at 112° C.

Into 3411 gm. of deionized water (50° C.) and 152 gm. ofdimethylethanolamine, 2,777 gm. of the resin mixture was slowly dropped.The dispersion formed easily and the constants of the dispersion aresimilar to those of the previous example.

Summary of Examples 6-10

The dispersions of Exs. 6-10 are each useful per se, and can beformulated with pigment solids, cross-linker, and other adjuvants tomake valuable coating compositions.

The resinous, film-forming solids in the dispersions of Examples 6through 10 have the compositions tabulated in Table 6 below.

                  TABLE 6                                                         ______________________________________                                        Step 4 Dispersion Products: Composition of Solids                                        Percentage by Weight                                               Component    Ex. 6   Ex. 7   Ex. 8 Ex. 9 Ex. 10                               ______________________________________                                        Epoxy Resin  74      67      76    70    70                                   Extender polymer:                                                             Polystyrene   4      --      --    --    --                                   Polybutene   --      16.5    --    --    --                                   Epoxidized   --      --       4.5  --    --                                   polybutadiene                                                                 Coumarone-   --      --      --    12    --                                   indene                                                                        Polybutadiene                                                                              --      --      --    --    12                                   Acrylic      22      16.5    19.5  18    18                                   ______________________________________                                    

Each of these dispersions contains sufficient epoxy resin for excellentadhesion to metal surfaces, and for the production of films having goodchemical inertness and hence good barrier properties. Moreover, thebalance of properties and the composition of each is such as to permitthe formulation of a sprayable sanitary coating composition withexcellent storage stability, good application properties, andoutstanding cured characteristics.

The amount of acrylic acid present is important since it imparts acidfunctionality and hence ionizability. The respective amounts ofmethacrylic acid (MAA) and of carboxyl group (COOH) are listed in Table7 below.

                  TABLE 7                                                         ______________________________________                                        Step 4 Dispersion Products: Methacrylic Acid and Carboxyl                     Components Percentage by Weight of Total Resinous Solids                             Ex. 6  Ex. 7  Ex. 8     Ex. 9                                                                              Ex. 10                                    ______________________________________                                        MAA      16.5     10.7   12.7    11.7 11.7                                    Carboxyl 8.6      5.6    6.6     6.1  6.1                                     ______________________________________                                    

THE IN SITU POLYMERIZATION STEP Example 11 Sprayable Can CoatingComposition Epoxy:Polystyrene:Acrylic

The dispersion of Ex. 6 was used for this demonstration of in situ vinyl(acrylic) polymerization for increasing the solids content.

2400 gms. of the dispersion, 174 gms. of styrene, 26 gms. of methacrylicacid, and 573 gms. of water were charged into a 5 liter round bottomflask equipped with a stirrer, N₂ inlet, thermometer and a condenser. Tothis reaction mixture was added 1.1 gms. of sodium formaldehydesulfoxylate in 10 gms. of DI water.

The reaction mixture was heated to 50° C., and then 1.1 gms. of t-butylhydroperoxide (t-BHP) (90% in water) in 10 gms. of DI water was added.The temperature was then raised to 80° C., and at that temperature thereactants were held for 1 hour. At the end of the 1 hour hold, 0.5 gms.of sodium formaldehyde sulfoxylate in 5 gms. of DI H2O, and 0.5 gms. oft-BHP in 5 gms. of water were added and held at 81° C. for 1/2 hour. Atthat time another shot of chaser (0.5 gms. of sodium formaldehydesulfoxylate in 5 gms. of water and 0.5 gms. of t-BHP in of water) wasadded, and the mixture was held for 11/2 hours at 81° C. At the end of1/2 hour, the non-volatiles were determined to be 24.06%. At the end of11/2 hours, the non-volatiles were determined to be 24.17%. 783 gms. ofDI water was then added.

The final constants for this material were:

NV=19.25 (30 min. 400° F.)

Viscosity=10 secs. #4 Ford dup

AN=88.2 on NV

BN=50.3 on NV

% neutralization=57%

The solids in this product are derived from the following sources, thenumbers representing proportions by weight:

    ______________________________________                                        epoxy resin          56                                                       polystyrene extender polymer                                                                        3                                                       monomer:                                                                      added during grafting                                                                              16                                                       added during in situ 25                                                       polymerization                                                                Total Monomer        41                                                       Total                100                                                      ______________________________________                                    

In ratio form, the solids composition can be described as:epoxy:polystyrene:acrylic=56:3:41.

This dispersion can be formulated with Cymel 303 aminoplast, up to about10% based on the dispersion, to form a sprayable, curable, clear cancoating. The coating can be opacified if desired, by the addition offrom about 1% to about 1.9% by weight of the dispersion of pigment gradetitanium dioxide.

Example 12 Sprayable Protective Coating; Epoxy:Polybutene:Acrylic

The dispersion of Ex. 7 was used as the vehicle for this demonstrationof in situ polymerization for solids augmentation.

2242 gms. of the dispersion, 800 gms. of DI water, 330 gms. of styrene,and 50 gms. of methacrylic acid were charged into a 5 liter round bottomflask, and heated to 50° C. 4 gms. of sodium formaldehyde sulfoxylate in40 gms. of DI water was then added to the reaction mixture, followed by4.4 gms. of t-butyl hydroperoxide (t-BHP) (90% in water) in 40 gms. ofDI water. The reaction temperature was then raised to 75° C. and held atthat temperature for 2 hours. At the end of the 2 hour hold, a chasercomposed of 2 gms. of sodium formaldehyde sulfoxylate in 20 gms. ofwater and 2.2 gms. of t-BHP in 20 gms. of water was added, and thereaction mixture was held for 1 hour at 75° C. At the end of that timethe chaser step was repeated. After another hour on hold, 36 gms. ofdimethyl ethanolamine and 32 gms. of water were added and held foranother hour at 75° C. The constants for the final material were:

NV=25.1%

AN=79.5

BN=51.4

Viscosity=15 secs. #4 Ford cup

OS/S=0.48

Epoxy:polybutene:acrylic=39:10:51

This dispersion can be formulated with pigment solids and a cross-linkerto form coating compositions that are useful for general purposeprotective and decorative coatings.

Example 13 Sprayable Coating Composition; Epoxy:EpoxidizedPolybutadiene:Acrylic

The dispersion of Example 8 was used as the vehicle for this in situpolymerization.

2260 gm. of the dispersion and 1200 gm. of deionized water were chargedinto a 5-liter round bottom flask equipped with a nitrogen inlet,condenser, thermometer and mechanical agitator. The mixture was heatedto 50° C. and a mixture of 330 gm. of styrene and 50 gm. of methacrylicacid was slowly added to the dispersion over a period of 1 hour.

After the monomer addition, 4 gm. of sodium sulfoxylate formaldehyde in40 gm. of water, and 4.4 gm. of t-BHP (90% in water) in 40 gm. of water,were added, and the temperature raised to 71° C. The temperature washeld at 71° C. for 2 hours, and a chaser of 2 gm. of sodium sulfoxylateformaldehyde in 20 gm. of water, and 2.2 gm. t-BHP in 20 gm. of water,was added. The reaction was held another hour at 71° C. At the end ofthat time, the chaser step was repeated. 36 gm. of dimethyl ethanolaminein 32 gm. of deionized water was then added and held another hour. 100gm. of n-butanol and 35 gm. of dimethylethanolamine were added.

The resulting dispersion had the following constants:

    ______________________________________                                        NV                21.4%                                                       Viscosity         355 sec. #4 Ford Cup                                        AN                83.6                                                        BN                88.6                                                        % neutralization  105%                                                        OS/S              0.68                                                        ______________________________________                                    

Example 14 Coating Composition; Epoxy:Coumarone-Indene:Acrylic

The dispersion of Ex. 9 was augmented in solids content, and itspercentage of organic solvent reduced, by the following operation.

2383 gm. of the dispersion from Ex. 9 and 1000 gm. of deionized waterwere charged into a 5-liter round bottom flask. The mixture was thenheated to 50° C. under agitation with a nitrogen sparge. A monomer mixconsisted of 330 gm. of styrene and 50 gm. of methacrylic acid was addedto the reaction mixture over an hour, followed by 4 gm. of sodiumsulfoxylate formaldehyde in 40 gm. of water and 4.4 gm. of t-BHP (90% inwater) in 40 gm. of water.

The temperature was raised to 76° C., at which temperature, the reactionmixture was held for 2 hours. At the end of the 2 hour hold, a chaser of2 gm. of the sodium sulfoxylate formaldehyde in 20 gm. of water and 2.2gm. of t-BHP (90% in water) in 20 gm. of water was added. The reactionwas held for another hour at 76° C. and the chaser step repeated. 36 gm.of dimethylethanolamine and 32 gm. of deionized water were added and thereaction mixture held for another hour.

The final dispersion has the following constants:

    ______________________________________                                        NV                21.6                                                        Viscosity         14 secs. (#4 Ford Cup)                                      AN                88.7                                                        BN                74.1                                                        % neutralization  83.5                                                        OS/S              0.54                                                        ______________________________________                                    

The proportion of epoxy to coumarone-indene to acrylic were about41:7:52. This dispersion was readily formulated into protective coatingsthat were particularly useful for metal surfaces. It could also be useddirectly for clear coatings, but more desirable application anddecorative properties were obtained by formulation with added water andpigment solids, and preferably, an aminoplast cross-linker.

Example 15 Coating Composition:Epoxy:Polybutadiene:Acrylic

The dispersion of Ex. 10 was augmented in solids content, and itspercentage of organic solvent reduced, by the following in situ vinylpolymerization.

To 2298 gm. of the dispersion of Ex. 10 was added 1200 gm. of deionizedwater. The mixture was heated under N2 blanket to 50° C. 330 gm. ofstyrene and 50 gm. of methacrylic acid were slowly added to thedispersion over a period of an hour, and 4 gm. of sodium sulfoxylateformaldehyde in 40 gm. of water was added followed by 4.4 gm. of t-BHP(90% in water) in 40 gm. of water. The resultant reaction mixture wasthen heated to 75° C. and held for 2 hours at that temperature. At theend of the hold, a chaser of 2 gm. of sodium sulfoxylate formaldehyde in20 gm. of water and 2.2 gm. of t-BHP (90% in water) in 20 gm. of waterwas added, and reaction mixture was held for one hour. At the end ofthat time, the chaser step was repeated. 36 gm. of dimethylethanolamineand 32 gm. of water was then added and the mixture held for another hourat 75° C.

The dispersion had the following constants:

NV: 23.2%

Viscosity: 27 secs. (#4 Ford Cup)

AN: 80.4

BN: 60.6

% neutralization: 75.3

OS/S: 0.5

Epoxy: acrylic: 41:7:52

n-butanol/2-butoxy-ethanol-1=75/25

The dispersion was useful for the same purposes as the product of Ex.14.

Summary of Examples 11-15

The resinous, film-forming solids of the dispersions of Examples 11through 15 have the compositions listed in Table 8 below.

                  TABLE 8                                                         ______________________________________                                        Step 5 Dispersion Products: Composition of Solids                             Percentage by Weight of Total Resinous Solids                                 Component    Ex. 11  Ex. 12  Ex. 13                                                                              Ex. 14                                                                              Ex. 15                               ______________________________________                                        Epoxy Resin  56      39      44.8  41    41                                   Extender polymer:                                                             Polystyrene   3      --      --    --    --                                   Polybutene   --      10      --    --    --                                   Epoxidized                                                                    Polybutadiene                                                                              --      --       2.7  --    --                                   Coumarone-Indene                                                                           --      --      --     7    --                                   Polybutadiene                                                                              --      --      --    --     7                                   Acrylic      41      51      52.5  52    52                                   Total MAA    20      12      12.9    12.3                                                                                12.3                               (Approx.)                                                                     Total Carboxyl                                                                             10       6       6.7    6.4   6.4                                (Approx.)                                                                     ______________________________________                                    

ALTERNATE PROCESS Example 16 The Third Preferred Embodiment Addition OfExtender Polymer Prior to the In Situ Polymerization

A 100 gallon reactor was charged with the following:

263 lb. of Dow DER-331 liquid epoxy resin

13.8 lb. xylene

149 lbs. of bisphenol A

75 lbs. of 2-butoxyethanol-1

It should be noted that DER-331 resin is essentially the same as theDER-333 resin used in the earlier examples, but lacks a self-containedcatalyst and xylene. The appropriate amount of xylene is added above tomake this resin have the same xylene content as DER-333 resin.

The mixture was heated to 185° F. and 55.8 gms. of sodium acetatetrihydrate in 539 gms. of DI H₂ O was added to the reaction mixture. Theheating was resumed at a vacuum of 20 inches was applied to the reactor.About 1/2 hour later, the temperature reached 310° F. At that time thevaccum was disconnected and a nitrogen sparge was inserted. Six lbs. ofvolatiles were collected at 320° F. The temperature was held at 350° F.for 2 hours. At the end of that time the viscosity of the reactionmixture was only V (40% NV in 2-butoxyethanol-1). Another shot ofcatalyst, 28 gms. of sodium acetate trihydrate in 280 gms. of DI water,was added below the surface. The reaction mixture was then held at 350°F. for another 4 hours. At the end of that time, the viscosity of theadvanced epoxy resin was Y (40% NV in 2-butoxyethanol-1).

At that time the reactor was sealed and 242 lbs. of n-butanol was pumpedinto the reactor below the surface. The temperature of the reactor wasallowed to drop to 235° F. (113° C.). After the n-butanol was added, amonomer mixture consisting of the following:

69 lbs. of methacrylic acid

36 lbs. of styrene

439 gms. (0.97 lbs.) of ethyl acrylate

9.4 lbs. of BPO (78% NV in H₂ O)

27 lbs. of 2-butoxyethanol-1

was added over a period of 2 hours. Once the monomer mixture was added,15 lbs. of n-butanol was added into the reactor through the monomer feedtank. The graft polymer resinous reaction product was then held at 237°F. (114° C.) for 3 hours. At the end of the hold, the viscosity wasobtained as M-N (1 pt. resin in 1 pt. N-methylpyrrolidone).

The resinous reaction product was then dropped into a reducing tank,over a period of about 1 hour. The reducing tank contained 1134 lb. ofDI water, 64 lb. of n-butanol, and 50 lb. of dimethyl ethanolamine. Thereducing tank components were heated to about 150° F. (65° C.) beforethe drop. After the resinous reaction product was dropped into thereducing tank, 160 lb. of DI water was added. The constants for thedispersion were:

NV=23.4%

AN=80.9

BN=58

Viscosity=72 secs. #4 Ford cup

OS/S=0.92

This dispersion was useful in its own right, in the formulation ofsprayable can coatings (see particularly related patent application Ser.No. 788,611). However, for present purposes, it was used to demonstratea variant embodiment of the present invention.

Thus, 2420 gms. of this dispersion, 716 gms. of DI water, 18 gms. ofdimethyl ethanolamine, 165 gms. of styrene, 25 gms. of methacrylic acid,and 190 gms. of polybutadiene (Lithene PL from Revertex Corp. England),were charged into a 5 liter round bottom flask equipped with agitator,N₂ inlet, condenser and a thermometer. The mixture was stirred for anhour and then heated to 55° C., 4 gms. of sodium formaldehydesulfoxylate in 40 gms. of DI water, and 4.14 gms. t-BHP in 40 gms. ofwater were added. The temperature was then raised to 75° C. and heldthere for 2 hours. After the end of two hours, a chaser of 2 gms. ofsodium formaldehyde sulfoxylate in 20 gms. of water and 2.2 gms. oft-BHP in 20 gms. of water was added to the reaction mixture and held for1 hour at 75° C. At the end of the hour hold, the chaser step wasrepeated.

The constants for the final material were:

NV=24.1%

AN=73.4

BN=56.4

Viscosity=15 sec. #4 Ford Cup

Epoxy: polybutadiene: Acrylic=47:20:33

This material made an excellent spray coating and was particularly wellsuited for formulation with cross-linkers and pigment.

This example was repeated twice with two different extender polymersrespectively. Considering the foregoing detailed demonstration asproducing a product dispersion 16A, a product 16B was similarly made bysubstituting as the extender polymer polybutene 24 from Chevron ChemicalCo., and a product 16C was similarly made by substituting as theextender polymer Cumar-R1, a coumarone-indene resin from NevilleChemical Co.

The constants and compositions for these three products were presentedfor comparison, as follows:

    ______________________________________                                                   Product                                                                       16A       16B       16C                                            ______________________________________                                        Properties                                                                    % Non-Volatile                                                                             24.1        23.9      23.5                                       Viscosity (#4 Ford                                                                         15 sec.     15 sec.   16 sec                                     Cup at 25° C.)                                                         Acid Number  73.4        73.8      75.7                                       Base Number  56.4        48.3      53.8                                       % Neutralization                                                                           76.8        65.5      71.1                                       Ratio of n-butanol                                                                         75/25       75/25     75/25                                      to 2-butoxyethanol-1                                                          OS/S          0.55        0.55      0.55                                      Composition                                                                   Epoxy        47          47        47                                         Extender Polymer                                                                           20          20        20                                         Acrylic      33          33        33                                         Type of Extender                                                                           Polybutadiene                                                                             Polybutene                                                                              Coumarone                                  Polymer                            Indene                                                                        Copolymer                                  ______________________________________                                    

Example 17 Coating Composition: Epoxy:Acrylic:Acrylic Addition ofAcrylic Extender Polymer Prior to the In Situ Polymerization

In this demonstration of the third preferred embodiment of theinvention, an acrylic copolymer is used as the extender polymer, and isformed in the presence of the earlier-formed graft polymer. The initialstep was that of advancing a liquid epoxy resin.

438 gms of a liquid epoxy resin (Epon 828), Shell Chemical Co., 248 gmsof Bisphenol A, 23 gms of xylene and 125 gms of 2-butoxy-ethanol-1, werecharged into a 5 liter round bottom flask equipped with a N₂ inlet,condenser, stirrer and a thermometer. The reaction mixture was heated to50° C., then a mixture of 0.32 g. of sodium acetate trihydrate and 3.6gms of water was added. When the temperature reached 120° C., a vacuumof 18" was applied to the reaction mixture and heating continued.

At 140° C. the heating was stopped and a small exotherm was observed.The vacuum was broken off. 23 gms of liquid had collected in the vacuumtrap. Heating was continued until the temperature reached 175° C. Atthat time the temperature was stabilized for 3 hrs. At the end of thattime, the viscosity of the resin mixture was Z₁ +1/2 (40% NV in2-butoxyethanol-1). 484 gms of n-butanol were then added slowly, and thetemperature was then stabilized at 110° C.

For the grafting step, a monomer mixture was made up of:

    ______________________________________                                                       Gms.                                                           ______________________________________                                        Methacrylic acid 114                                                          Styrene          60                                                           Ethyl acrylate   1.6                                                          BPO              15.5                                                         2-butoxyethanol-1                                                                              45                                                           ______________________________________                                    

This mixture was slowly added over a two hour period to the resin basewhile maintaining the temperature of the resin at 110° C. 25 gms ofn-butanol were then added and the reaction mixture was held at 110° C.for 3 hours.

To add the extender polymer at this point, preparations were made toform an acrylic copolymer in the presence of the graft polymer preparedin the preceding reaction. To this end, a monomer mixture was made upof:

    ______________________________________                                                       Gms.                                                           ______________________________________                                        Styrene          1238                                                         Methacrylic acid 185.5                                                        BPO               9.1                                                         n-Butanol        436                                                          2-butoxyethanol-1                                                                              172                                                          ______________________________________                                    

This mixture was added over 21/2 hrs. to the graft polymer-containingreaction mixture while the temperature was held at 110° C. After theaddition was completed, 47 gms of n-butanol was added and the reactionmixture was held another 2 hrs. at 110° C. At the end of the 2 hr. holdperiod, a chaser which contained 9.1 gms of BPO and 20 gms xylene wasadded, and the reaction mixture was then held for another hour. Themixture of acrylic copolymer-extender and of graft polymer resinousreaction product was then ready to be dispersed in water. The resinviscosity was M^(1/2) as measured by dissolving 1 part of the resinsolution in 1 part of N-methyl pyrrolidone.

Only a portion of the resin solution was dispersed in water. Thus, 2747gms of the resin solution was slowly dropped into an aqueous mixturecomposed of 3911 gms of deionized water and 152 gms of dimethylethanolamine. The constants for the aqueous dispersion were:

NV=21.1%

AN=93.8

BN=64.9

Viscosity=3 min. #4 Ford Cup

OS/S=0.69

To carry out the in situ vinyl polymerization step, 2592 gms of theabove dispersion, 165 gms of styrene, and 25 gms of methacrylic acidwere charged into a 5 liter round bottom flask equipped with a stirrer,N₂ inlet, thermometer and a condenser. To this reaction mixture 0.95 gmsof sodium formaldehyde sulfoxylate in 20 gms of DI water was added.

The reaction mixture was heated to 50° C. and then 2.1 gms of t-butylhydroperoxide (90% in water) in 20 gms of DI water was added. Thetemperature was then raised to 80° C. and at that temperature thereaction mixture was held for 1 hour. At the end of the 1 hour holdperiod, a chaser, which contained 0.19 gms of sodium formaldehydesulfoxylate in 10 gms of DI water and 0.21 gms of t-BHP in 10 gms ofwater, was added, and the contents of the flask were held at 80° foradditional 1 hour.

At the end of second hold period, a second chaser was added, and held at80° for another hour. Then 18 gms of dimethyl ethanolamine and 16 gmswater were added, and the reaction mixture was held for 1 more hour.Then the heat was turned off and the reaction mixture was cooled to roomtemperature while stirring. The final constants for this material were:

NV=25.0%

AN=86.0

BN=62.4

Visc.=42 sec. #4 Ford Cup

This dispersion was useful as a sprayable, water-reducible coatingcomposition. The Acid Number is adequate to maintain the solidsdispersed over long storage periods, with substantially no settling orchange in viscosity or pH. This formulation is a particularly remarkableachievement, since the contribution of the epoxy resin to overall finalsolids content is below 25% by weight. The acrylic extender provides themajor contribution to the solids (in the neighborhood of two-thirds byweight).

Conclusion

Compositions prepared in accordance with the present invention areuseful directly as coating compositions, or as the base from whichcoating compositions can be formulated. However, in its preferredembodiments, the invention is concerned with the formulation ofwater-reducible, sprayable compositions that can be used for coatingcans for beverages, especially beer cans.

Such coatings prepared in accordance with the invention can beformulated to offer economy, relatively low ratio of organic solvents tosolids (an important environmental consideration), and the achievementof sprayable consistencies with the least organic solvent contentfeasible. Moreover, such coatings can be formulated to exhibit littlediscernible change in either viscosity or pH after extended roomtemperature storage, indicating the absence of gelation and theexistence of "stable" dispersions (as that term is used herein).

Beer can coating compositions prepared in accordance with preferredembodiments of the present invention can be formulated to exhibit goodstability, turbidity resistance, blush properties, and adhesion to cans,whether made of aluminum, steel, tin plate, or other material. Suchcoating compositions can be formulated to cure in a few seconds at 450°F. or so (about 230° C.), and also at lower temperatures such as 350° F.(177° C.), and to exhibit superior properties as to resin volatilization(fuming). When filled, a properly coated can may be exposed to elevatedtemperatures, as during pasteurization, without blush. Properly coatedcans prepared from preferred and appropriate formulations impart littleor no taste to the beverage, and the beverage should not developundesirable flavor notes, turbidity, or haze.

In addition, the coatings can be formulated to permit the necessaryforming operations to be accomplished on the coated metal substantiallywithout the development of cracks, pin-holes, or the like. Preferredcoatings are resistant to pasteurization temperatures and aresubstantially free of components that might migrate into the beverageduring pasteurization or storage.

While compositions prepared in accordance with the invention areprimarily intended for use as liquid coatings, they may be reduced topowders for application or for reconstitution to flowable form.

The process of the invention can make more efficient use ofmanufacturing equipment per unit of solids sold, and thus can reducecosts and the need for additional reactor capacity.

While the grafting and in situ polymerization steps have been describedand exemplified herein as each comprising a single polymerization step,there may be two or even more successive such polymerizations for eachsuch step, depending upon the final properties and compositions desired.

Water dispersion sanitary coating compositions made in accordance withpreferred embodiments of this invention can be formulated to performwell when sprayed by both air and airless devices, with atomizationbeing obtainable with any type of nozzle or pressure, that is, sprayingapplications can be made at pressures in the range from 2 psi up to1,500 psi. These compositions generally have excellent applicationproperties, and generally their use is free from problems with respectto blistering, sagging, solvent washing, foaming, and excess flow.

Coating materials made in accordance with the invention can be appliedto tin plate, aluminum, and to metal coated with primers, in a range ofapplication thicknesses producing cured weights per 12-ounce can in therange from 1 to 10 mgs/in, which is 50 to 300 mgs. per 12-ounce can.Film continuity generally is readily attainable throughout this range.

While the invention has been disclosed by reference to the details ofpreferred embodiments thereof, it is to be understood that suchdisclosure is intended in an illustrative rather than in a limitingsense, and it is contemplated that various modifications in thecompositions and processing techniques, in particular, will readilyoccur to those skilled in the art, within the spirit of the inventionand within the scope of the appended claims.

What is claimed is:
 1. A process comprising reacting:(a) a tractablegrafting base comprising:(i) a 1,2-epoxy resin having an epoxyequivalent weight of at least 500 and (ii) a second, extender polymerselected from polystyrene, low molecular weight polyethylene,styrene-acrylate copolymer, ethylene-vinyl acetate copolymer, a hydroxylterminated polyester or polyurethane, styrene-acrylonitrile copolymer, ahydrocarbon resin, a second epoxy resin, or a mixture thereof; said 1,2epoxy resin and said extender polymer having aliphatic backbone carbonatoms including carbons having only one or two hydrogens bonded thereto,each of said 1,2 epoxy resin and said extender polymer contributing atleast 10% by weight of the total solids present, and (b) vinyl monomerthat is addition polymerizable through its ethylenic unsaturationselected from ethylenically acrylic or methacrylic acid, styrene,ethylenically unsaturated acid esters, or mixtures thereof; and in thepresence of a free radical initiator that is characterized by itsability to abstract hydrogen, at a temperature and in sufficientquantity that said initiator is operative simultaneously to causeaddition polymerization of the monomer and to cause graft polymerizationby carbon-to-carbon bonds of addition polymer to at least some of saidaliphatic backbone carbons that have one or two hydrogens bonded theretoin the ungrafted state.
 2. The process of claim 1 wherein the epoxyresin is an adduct of a bisphenol and a diglycidyl ether of a bisphenoland wherein said adduct has an epoxy equivalent weight of at least 2,000and constitutes at least 45% of the grafting base by weight.
 3. Theprocess of claim 2 wherein the epoxy resin is one that has been advancedin the presence of the extender polymer.
 4. The process of claim 1wherein the vinyl monomer includes an acrylic acid in sufficientquantity to establish the resinous product as a dispersion in a basicaqueous medium.
 5. The process of claim 1 wherein said ethylenicallyunsaturated compound comprises an unsaturated primary or secondaryamine, present in sufficient quantity to establish the resinous reactinproduct as a dispersion in an acidic aqueous medium.
 6. The process ofclaim 1 wherein said ethylenically unsaturated compound comprises acompound having in its molecule an epoxy group that can be rendered basefunctional by reaction with a primary or secondary amine.
 7. A resinousreaction product comprising a mixture of resinous solids, said solidsbeing made up of components comprising:(i) addition polymerizablemonomer selected from ethylenically acrylic or methacrylic acids,styrene, ethylenically unsaturated acid esters, or mixtures thereof;(ii) an aromatic 1,2-epoxy resin having an epoxy equivalent weight of atleast 500; (iii) an extender polymer selected from polystyrene, lowmolecular weight polyethylene, styrene-acrylate copolymer, anethylene-vinyl acetate copolymer, a hydroxyl terminated polyester orpolyurethane, styrene-acrylonitrile copolymers, hydrocarbon resin, asecond epoxy resin, or mixtures thereof; wherein each of said 1,2-epoxyresin and said extender polymer have aliphatic backbone carbon atomsthat have one or more hydrogens bonded thereto, and (iv) graft polymersof each of the epoxy resin and the extender polymer in which additionpolymer side chains are grafted by carbon-to-carbon bonds to at leastsome of said aliphatic backbone carbon atoms of the resin and of thepolymer that had one or two hydrogens bonded thereto in the ungraftedstate.
 8. The resinous reaction product of claim 7 wherein the solidsinclude a sufficient number of ionizable sites to establish the reactionproduct as a dispersion in an aqueous ionizing medium.
 9. The resinousreaction product of claim 8 wherein the ionizable sites are located inthe side chains of said graft polymers and in said addition polymerizedmonomer.
 10. The reaction product of claim 9 wherein the solids are acidfunctional and wherein the acid-functionality is sufficiently high toestablish the resinous reaction product as a dispersion in a basicaqueous ionizing medium.
 11. The resinous reaction product of claim 9wherein the solids are base functional and wherein the basefunctionality is sufficiently high to establish the resinous reactionproduct as a dispersion in an acidic aqueous ionizing medium.